94 Physiology, Biochemistry and Pharmacology

Reviews of 94 Physiology, Biochemistry and Pharmacology

Editors R. H. Adrian, Cambridge. H. zur Hausen, Freiburg E. Helmreich, Wtirzburg • H. Holzer, Freiburg R. Jung, Freiburg • O. Krayer, Boston R. J. Linden, Leeds. P. A. Miescher, Gen6ve J. Piiper, G6ttingen • H. Rasmussen, New Haven U. Trendelenburg, Wiirzburg • K. Ullrich, Frankfurt/M. W. Vogt, G6ttingen. A. Weber, Philadelphia

With 52 Figures

Springer-Verlag Berlin Heidelberg New York 1982 ISBN 3-540-11701-6 Springer-Verlag Berlin Heidelberg NewYork ISBN 0-387-11701-6 Springer-Verlag NewYorkHeidelberg Berlin

Library of Congress-Catalog-Card Number 74-3674 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustra- tions, broadcasting, reproduction by photocopying machine or similar means, and stor- age in data banks. Under § 54 of the German Copyright Law where copies are made for other than private use, a fee is payable to 'Verwertungsgesellschaft Wort', Munich. © by Springer-Verlag Berlin Heidelberg 1982 Printed in Germany. The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Offsetprinting and Binding: Konrad Triltsch, Wtirzburg 2127/3130-543210 Contents

Obituary Joshua Harold Burn (1892-1981) By M. VOGT, Cambridge/Great Britain. With 1 Figure ...... 1

Cardiovascular Sympathetic Afferent Fibers By A. MnLLIANI, Milan/Italy. With 30 Figures 11

The Functions of the Renal Nerves By G. F. DIBoNA, Iowa City, Iowa/USA. With 21 Figures ...... 75

Author Index ...... , ...... 183

Subject Index ...... 203

Indexed in Current Contents Obituary Joshua Harold Burn (1892-1981) 2 M. Vogt

With the death, on 13 July 1981, of Professor Joshua Harold Burn, pharmacological science lost a leader, medical and science students an eminent teacher, and pharmacologists everywhere a personal friend. Just before his 89th birthday, which was on 6 March 1981, his health started to deteriorate, but up to that time his interest in his own science, in local history, architecture and art remained lively, and he was able to enjoy sharing his cultural interests with Elizabeth Haslam-Jones, whom he had married in 1971. His first wife died in 1927, and his second in 1971. There are two sons and four daughters from these two marriages; two daughters are married and living in the U.S.A. Burn was born in Barnard Castle, Co. Durham, in 1892, and spent his school years there. He was the only child of J.G. Burn, who was the head of a family grocery business. His mother, a doctor's daughter, was described as "lively, cheerful and energetic". Burn's interest in science may have been aroused at school, since he later commented on its well-equip- ped chemistry and physics laboratories and its excellent teacher in chemistry. On leaving school, Bum won a scholarship for Cambridge and entered Emmanuel College in October 1909; his tutor was F.G. Hopkins. In 1912 he took first class honours in part II of the tripos in physiology. Having been awarded a research grant by Emmanuel College, and the Michael Foster Studentship by the University, he started work with Joseph Barcroft in the Physiology Department. The results of his experiments on the oxygen capacity of the blood, showing that it remains unaffected by dilution, were published in the Journal of Physiology in 1913. On 1 Janu- ary 1914 he moved to London to take up employment as a pharmacologist in the Wellcome Physiological Laboratories. He began working with H.H. Dale, but war broke out and he spent from October 1914 to 1918 in the army. After the war, he completed his medical training at Guy's Hospital, London. In September 1920 he rejoined Dale, who had become Director of the National Institute for Medical Research in Hampstead, and remained there till 1925. This was also the year in which he took his M.D. degree and was awarded to Horton Smith prize for his dissertation. The publications from the years in Hampstead presage interests which recurred in later years. Two papers deal with sweating: one with its relation to blood flow and nerve supply, and the other with the action of pilocarpine. A first report on biological standards, by Burn and Dale, appeared in 1922. It is interesting that an entire series of papers, centred around insulin, deal not with its assay but with attempts at clarifying its mode of action. On 1 January 1926 Burn became director of the Pharmacological Laboratories of the Pharmaceutical Society, in those days located in Obituary Joshua Harold Burn 3

Bloomsbury Square, London. He held this post for 12 years, during which period he was made professor of pharmacology at the University of London, in 1933. His papers till 1930 show the great effort he put into devising methods of standardization. One of the tasks of the Pharmaceutical Society was to check on the suitability for patients of galenical preparations, vitamins and hormones, the composition of which could not be assessed by chemical means. Tests on isolated organs and small animals had to be made, and sound statistical principles applied. Burn's two books, Methods of Biological Assay (1928), and Biological Standardization (1937), have guided innumerable readers in the application of reliable methods. While chemical means of testing have since become possible for some of the substances discussed in these books, it is important to remember that some of the tests described remain useful in estimating the therapeutic action of newly developed drugs. This is why the 1950 edition of Biological Standardization should, as Burn states in its preface, really have been entitled "Quantitative Methods in Pharmacology and Chemotherapy". From 1930 onward, Bum's interest in the function and actions of the autonomic nervous system and their modification by endogenous or exogenous substances became increasingly obvious. 1930-1933 was also the period in which he showed conclusively that the sympathetic nerves are capable of taking up adrenaline from the circulation, thus "replenishing their stores" and improving their performance whenever this has been impaired by lengthy experimental procedures, as for example, in pump per- fusions of isolated organs. This uptake process later gained great importance when drugs capable of impairing it were discovered. The expression of Bum's scientific interests was helped immensely by the arrival in his laboratory in 1933 of Edith Biilbring, a pharmacologist who had worked in Paul Trendelenburg's Institute in Berlin till his untime- ly death. In 1935/6 five joint papers by Bfilbring and Burn appeared in the Journal of Physiology, several of these on sympathetic vasodilators. Then both authors moved to Oxford, where Burn occupied the chair in Pharma- cology from 1937 till his retirement in 1959. It was in Oxford that Burn expanded to the full an activity which has been of the greatest importance to progress in pharmacology all over the world. In addition to having attracted a staff whose multidisciplinary expertise greatly widened the scientific scope of the laboratory, he continued and extended the excellent training of young pharmacoloists that he had begun in London. The novice was given a problem, had to learn the appropriate technique(s), and was visited daily by Burn, who wanted to see what results he or she was getting. The regular visits, and the lunch-time discussions of the work, were the expression of Burn's boundless enthusiasm for the subject and of his personal concern for the progress of his charges. 4 M. Vogt

Over the years about 200 scientists worked in Burn's Oxford laboratory. Some (H. Blaschko, E. Btilbring, D.B. Hope, H.R. Ing, H.W. Ling, E.M. Vaughan Williams and J.M. Walker) were on the staff and either are still there or remained in the Department till retirement, but the others were either beginners in training, or well-known scientists spending periods ranging from months to several years at Oxford. No other Depart- ment in Britain did as much as the one at Oxford, under Burn's professor- ship, for the training of future pharmacologists. Although these activities were somewhat restricted during the war years, they benefited colleagues in all parts of the world when international relations were restored. Outstanding among the publications of the war years is the first evidence of release of acetylcholine from the central nervous system; it was obtained on the perfused spinal cord of the dog (B/ilbring and Burn 1941). Before that, a recurring theme had been the modification of skeletal muscle activity by adrenaline, and by vasodilator nerves found in some species, particularly in the hare. Another topic concerned the smooth muscle of the nictitating membrane and the effect of denervation, which made the membrane highly sensitive to adrenaline, but lowered only very slightly, if at all, the threshold for tyramine (Biilbring and Burn 1938). It took two decades to reach a clear understanding of that difference (see below). Many striking observations were made by Burn and his co-workers on the fact that the actions of acetylcholine and adrenaline vary with the dose and the condition of the tissue. Since we have learnt in recent years about multiple, and particularly about pre-synaptic, receptors, these phenomena have become less of a mystery, but their demonstration in Burn's laboratory preceded their general recognition and explanation by many years. Interspersed among these academic papers were frequent articles written by Burn for the medical practitioner or the lay public. He wrote on asthma, on blood-pressure control, on antihistamines, on the evils of smoking, on fine chemicals in medicine and on the use of insecticides. He was as keen on preventing illness as on healing it, and had strong views on the beneficial effects of simple measures such as "an apple a day"; he was very persuasive on the power of cod-liver oil (not the more palatable halibut-liver oil) to prevent bronchitis in the elderly. In 1946, yon Euler found that sympathetic nerves, contain noradrenaline, and in the following year, Gaddum and Goodwin obtained the release of noradrenaline by stimulation of the cat's hepatic nerves. The question whether the adrenal medulla might secrete noradrenaline as an admixture to adrenaline was answered by Bfilbring and Burn in 1949. They stimulated the splanchnic nerves of the cat and tried to match the effects on the blood pressure, the innervated and the denervated nictitating Obituary Joshua Harold Burn 5 membranes, with injections of either adrenaline or noradrenaline, or a mixture of the two. Only a mixture of the two catecholamines reproduced the effect of splanchnic nerve stimulation, indicating that the adrenal secreted both compounds. The next years brought much work on the synthesis and stability of catecholamines. Furthermore, the suggestion was made that the hypersensitivity of denervated iris and blood vessels to catecholamines might be due to a loss of amine oxidase. However, when the experiments were repeated on a large number of animals, the results were inconsistent and the suggestion was abandoned [Bum, Philpot and Trendelenburg (1954) Br J Pharmacol 9:4231. There were investigations of the actions of acetylcholine and eserine, particularly in situations when acetylcholine is not a transmitter of nerve impulses. This led to papers on its role in ciliary movement and in auricular fibrillation of the artificially driven heart. In the heart, acetylcholine release was always found to be linked to the beat, and therefore considered to be essential to rhythmic activity. Auricular and ventricular fibrillation, their origin, experimental production and response to drugs, was a prominent topic in 1956 and 1957. New ideas and concepts started to appear in the following 2 years. In 1953, a publication (with Fleckenstein) dealt with the classification of sympathomimetic amines on the basis of whether or not their action on the nictitating membrane was enhanced or abolished by denervation. When reserpine, which removes catecholamines from nervous tissue without causing permanent damage, became available a few years later, the results of its administration were found to resemble those of denervation: tyramine lost its effect and noradrenaline became more potent. Both changes were abolished by an infusion of noradrenaline. The suggestion (Burn and Rand 1958) was that tyramine and congeners acted by releasing endogenous noradrenaline. The supersensitivity to noradrenaline after reserpine had its counterpart in the supersensitivity of denervated tissues. The observations on the nictitating membrane were equally valid for other sympathetically innervated tissues, the blood vessels being the most important from the clinical point of view. New findings which were to dominate Bum's future thinking were published in his paper with Leach, Rand and Thompson (1959) entitled "Peripheral Effects of Nicotine and Acetylcholine Resembling those of Sympathetic Stimulation". The authors saw this resemblance in pilomotor muscles, nictitating membrane and rabbit ear vessels, and noticed that all effects were greatly reduced by administration of reserpine or by denervation. The next step (Bum and Rand 1960) was to characterize the residual response to stimulation of postganglionic sympathetic fibres of animals treated with reserpine: the responses were all enhanced by eserine and abolished by atropine. There were obviously cholinergic fibres running 6 M. Vogt in the sympathetic nerve supply. Seeing an analogy to the situation in the adrenal medulla, where a cholinergic nerve impinges on the chrom- affin cell, Burn suggested that cholinergic nerves caused the release of noradrenaline from the sympathetic terminals, and postulated that noradrenergic fibres depend for their activity on first being primed by acetylcholine. This view, also known as the "theory of Burn and Rand", prompted a great number of very valuable investigations of peripheral sympathetic activity, both by Burn and by those who did not accept his conclusions. We owe a great increase in knowledge of the autonomic system to this controversy, but for Burn it was a cause of unhappiness, because he had hoped for acceptance without reservation. In many ways he was ahead of his time, as in his suggestion that nerve fibres may contain more than one transmitter; although we have no evidence that noradrenaline and acetylcholine coexist in the same (adult) neuron, recent work on peptides has shown that monoamines can co-exist, and be released, together with peptides. Burn also demonstrated that cholinergic fibres are much more widespread in postganglionic sympathetic nerves than had ever been suspected. What many colleagues found difficult to accept, however, was Burn's disagreement with the view that the adrenergic fibre may liberate "noradrenaline in the same way as cholinergic fibres liberate ACh". His hypothesis implied that adrenergic fibres liberate noradrenaline exclusively through the "cholinergic link". Support for this extreme view was obtained by Chang and Rand (1960) 1 who abolished the effect of sympathetic stimulation in several organs by hemicholinium, and restored the effect by giving choline. Yet the theory that the cholinergic link is always involved when noradrenaline is being released is not proven; Consolo et al. 2, for example, did not find evidence for this existence of cholinergic neurons in the spleen and the iris of the cat. A most interesting offshoot of this controversy is a paper on the phylo- genetic and ontogenetic development of the response of the intestine to stimulation of its periarterial nerves (Burn 1968). This was Burn's last experimental paper; the work was carried out partly in Philadelphia and partly in Harrogate, since Burn had no laboratory facilities in Oxford. It showed that in the adult fowl, in contrast to the adult mammal, stimulation of the periarterial fibres of the gut causes contraction, as does ACh. In the new-born rabbit, as in the adult fowl, contraction is elicited, but the response changes to relaxation between the ages of 3 and about 8 days.

1 Br J Pharmacol (1960) 15:588-600. Transmission failure in sympathetic nerves produced by hemicholinium. 2 Consolo S, Garattini S, Ladinsky H, Thoenen H (1972) J Physiol (Lond) 220:639- 646. Effect of chemical sympathectomy on the content of acetylcholine, choline and acetyltransferase activity in the cat spleen and iris. Obituary Joshua Harold Burn 7

Burn was a skilled and imaginative experimenter and a master of difficult perfusion techniques, and he enriched pharmacological knowledge over many decades. Interpretation of some of his results would have required knowledge of the multiplicity of receptors, and structural analysis by the electron microscope, neither of which were available during the period of his scientific acitivity. The areas of research for which Burn would probably have liked to be remembered are suggested in his last two published lectures (1976 and 1977): the uptake of catecholamines by sympathetic neurons; the development of an adrenergic from a cholinergic fibre; and the synergism of acetylcholine and noradrenaline in the activity of the postganglionic sympathetic neuron ("the cholinergic link"). Burn had strong views on many subjects, moral as well as scientific. He always stood up for his convictions, irrespective of whether it would have been to his advantage not to express them. His helpfulness knew no bounds, and was most frequently offered to his many young visitors and their families. What some newcomers to the laboratory regarded as his strictness originated in his concern and feeling of responsibility for the future of the younger generation. He had strong views about minor issues as well as about moral priorities. To quote from the preface to The Back- ground of Therapeutics (1948): "The care for a sick man in a bed is a good thing, but it is better to strive constantly to improve diagnosis and treatment in order to benefit one hundred other sick men who will occu- py the bed after he has gone." His objections to smoking and to beards were openly admitted. Whoever wishes to enjoy his irrepressible sense of humor should read "Essential Pharmacology" (Burn 1969) where the following passage describes his impressions on entering Emmanuel College, Cambridge: "I discovered that, compared with those who taught physiology and physics, the chemists were an unattractive lot, particularly those who demonstrated in the practical class. These seemed very undistinguished, had cheerless faces and wore rather shabby clothes." Writing came easily to Burn, and he found time in the evening to write many books. In addition to one pamphlet not connected with science, "A defence of John Balliol", he published eleven books, some addressed to scientists, others to the general public. The subjects range from bio-assays, biological standardization, therapeutics and practical pharmacology to the autonomic nervous system and medicine in general. In 1964 his last book appeared, characteristically entitled Our Most Interesting Diseases. Burn received honorary degrees from Yale, Mainz, Paris and Bradford Universities; the Schmiedeberg Plakette from the German Pharmacological Society; and the first Wellcome gold medal from the British Pharmacologi- cal Society - both societies also conferred honorary membership on him. He was an honorary member of the Czechoslovakian Medical Society of 8 M. Vogt

J.E. Purkinje, a member of the Deutsche Akademie der Naturforscher Leopoldina, and a Fellow of the Indian National Science Academy. He became a Fellow of the Royal Society in 1942. A last quotation from Bum's 1969 article in the Annual Review of Pharmacology may end this biographical sketch. In answer to the question whether he would choose a different career if he had his time again, his reply was, "I am quite certain that I would choose to have it all over again."

Bibliography

Books

Burn JH (1928) Methods of biological assay. Oxford University Press, London Burn JH (1937) Biological standardization. Oxford University Press, London Burn JH, Withell E R (eds) (1939) Whitla's pharmacy, materia medica and therapeutics. Bailliere Tindall & Cox, London (lst edn 1882) Burn J H (1948) The background of therapeutics. Oxford University Press, London Burn JH (1948) Lecture notes on pharmacology. Blackwell Scientific Publications, Oxford Burn JH (1952) Practical pharmacology. Blackwell Scientific Publications, Oxford Burn JH (1956) Functions of autonomic transmitters. Williams & Williams, Baltimore Burn JH (1957) The principles of therapeutics. Blackwell Scientific Publications, Oxford Burn JH (1962) Drugs, medicines and man. George Allen & Unwin, London Burn JH (1963) The autonomic nervous system. Blackwell Scientific Publications, Oxford Burn JH (1964) Our most interesting diseases. Charles Scribner's Sons, New York

Selected Papers

Burn JH (1913) The oxygen capacity of blood considered in relation to the concentration of haemoglobin. J Physiol (Lond) 45:482-488 Burn JH, Dale HH (1915) The action of certain quaternary ammonium bases. J Pharmacol Exp Ther 6:417-438 Burn JH (1922) The relation of nerve supply and blood flow to sweating produced by pilocarpine. J Physiol (Lond) 56:232-247 Burn JH, Dale HH (1922) Reports on biological standards. I. Pituary extracts. Medical Research Council. His Majesty's Stationary Office, London Burn JH, Dale HH (1924) On the location and nature of the action of insulin. J Physiol (Lond) 59:164-192 Burn JH (1925) The secretion of sweat and vasodilatation produced by pilocarpine. J Physiol (Lond) 60:365-378 Bourne A, Burn JH (1927) The dosage and action of pituary extract and of the ergot alkaloids on the uterus in labour, with a note on the action of adrenaline. J Obstet Gynaecol Brit Emp 34:249-272 Trevan JW, Boock E, Burn JH, Gaddum JH (1928) The pharmacological assay of digitalis by different methods. Quart J Pharm Pharmacol 1:6-22 Obituary Joshua Harold Burn 9

Burn JH (1929) The oral administration of powdered ergot. Quart J Pharm Pharmacol 2:515-524 Burn JH (1930) The estimation of digitalis by pigeon emesis and other methods. J Pharmacol Exp Ther 39:221-240 Bourne AW, Burn JH (1930) Action on the human uterus by anaesthetics and other drugs commonly used in labour. Br Meal J II:87-89 Burn JH, Tainter ML (1931) An analysis of the effect of cocaine on the actions of adrenaline and tyramine. J Physiol (Lond) 71 : 169-193 Burn JH (1932) The action of tyramine and ephedrine. J Pharmacol Exp Ther 46: 75-95 Burn JH (1932) On vasodilator fibres in the sympathetic, and on the effect of circulating adrenaline in augmenting the vascular response to sympathetic stimulation. J Physiol (Lond) 75:144-160 Bfilbring E, Burn JH (1936) The Sherrington phenomenon. J Physiol (Lond) 86:61- 76 Biilbring E, Burn JH (1936) Sympathetic vasodilatation in the skin and the intestine of the dog. J Physiol (Lond) 87:254-174 Btilbring E, Burn JH (1936) Sympathetic vasodilator fibres in the hare and the monkey compared with other species. J Physiol (Lond) 88:341-360 Biilbring E, Burn JH (1938) The action of tyramine and adrenaline on the denervated nictitating membrane. J Physiol (Lond) 91:459-473 Burn JH (1938) Sympathetic vasodilator fibres. Physiol Rev 18:137-153 Btilbring E, Burn JH (1939) Vascular changes affecting the transmission of nervous impulses. J Physiol (Lond) 97:250-264 Btilbring E, Burn JH (1940) The effect of sympathomimetic and other substances on the contraction of skeletal muscle. J Pharmacol Exp Ther 68:150-172 Btilbring E, Burn JH (1941) Observations bearing on synaptic transmission by acetylcholine in the spinal cord. J Physiol (Lond) 100:337-368 Biilbring E, Burn JH (1942) An action of adrenaline on transmission in sympathetic ganglia, which may play a part in shock. J Physiol (Lond) 101:289-303 Burn JH, Truelove LH, Burn I (1945) The antidiuretic action of nicotine and of smoking. Br Med J 1:403-409 Biilbring E, Burn JH, Skoglund CR (1948) The action of acetylcholine and adrenaline on flexor and extensor movements evoked by stimulation of the descending motor tracts. J Physiol (Lond) 107:289-299 B~ilbring E, Burn JH (1949) Liberation of noradrenaline from the adrenal medulla by splanchnic stimulation. Nature 163:363 Burn JH, Hutcheon DE, Parker RHO (1950) Adrenaline and noradrenaline in the suprarenal medulla after insulin. Br J Pharmacol 5:417-423 Burn JH, Langeman H, Parker RHO (1951) Noradrenaline in the whale suprarenal medulla. J Physiol (Lond) 113:123-128 Blaschko H, Burn JH, Carter CW (1951) L-Dopa decarboxylase and pressor amine formation in the adrenal medulla. J Physiol (Lond) 115:37P-38P Kordik P, Biilbring E, Burn JH (1952) Ciliary movement and acetylcholine. Br J Pharmacol 7:67-79 Burn JH, Robinson J (1952) Effect of denervation on amine oxidase in structures innervated by the sympathetic. Br J Pharmacol 7:304-318 Burn JH, Kottegoda SR (1953) Action of eserine on the auricles of the rabbit heart. J Physiol (Lond) 121:360-373 Fleckenstein A, Burn JH (1953) The effect of denervation on the action of sympathomimetic amines on the nictitating membrane. Br J Pharmacol 8:69-78 Burn JH (1953) Acetylcholine and the heart beat. Lancet I:l 161-1164 Biilbring E, Burn JH, Shelley HJ (1953) Acetylcholine and ciliary movement in the gill plates ofMy~'lus edulis. Proc R Soc Lond (Biol) 141:445-466 10 M. Vogt: Obituary Joshua Harold Burn

Burn JH, Trendelenburg U (1954) The hypersensitivity of the denervated nictitating membrane to various substances. Br J Pharmacol 9:202-209 Burn JH, Vaughan Williams EM, Walker JM (1955) The effects of acetylcholine in the heart-lung preparation including the production of auricular fibrillation. J Physiol (Lond) 128:277-293 Burn JH, Vaughan Williams EM, Walker JM (1956) The formation of acetylcholine in the heart; its effect on the systemic output and its importance for auricular fibrillation caused by aconitine. J Physiol (Lond) 131:317-328 Holland WC, Burn JH (1957) Production of fibrillation in isolated atria of rabbit heart. Br Meal J I:1031-1033 Burn JH, Rand MJ (1957) Reserpine and noradrenaline in artery walls. Lancet II: 1097 Burn JH, Rand MJ (1958) Excitatory action of the vagus in the isolated atria in relation to adrenaline. J Physiol (Lond) 142:173-186 Burn JH, Rand MJ (1958) The action of sympathomimetic amines in animals treated with reserpine. J Physiol (Lond) 144:314-336 Burn JI-I, Rand MJ (1959) The cause of the supersensitivity of smooth muscle to noradrenaline after sympathetic degeneration. J Physiol (Lond) 147:135-143 Burn JI-I, Leach EI-I, Rand MJ, Thompson JW (1959) Peripheral effects of nicotine and acetylcholine resembling those of sympathetic stimulation. J Physiol (Lond) 148:332-357 Burn JH, Rand MJ (1959) The sympathetic adrenergic mechanism. Nature 184:163- 165 Burn JI-I, Rand MJ (1960) Sympathetic postganglionic cholinergic fibres. Br J Pharma- col 15:56-66 Burn JI-I (1961) A new view of adrenergic nerve fibres explaining the action of reserpine, bretylium and guanethidine. Br Med J I: 1623-1627 Burn JH, Ng KKF (1965) Action of pempidine and antiadrenaline substances at the sympathetic postganglionic termination. Br J Pharmaco124:675-688 Burn JI-I, Gibbons WH (1965) The release of noradrenaline from sympathetic fibres in relation to calcium concentration. J Physiol (Lond) 181:214-223 Burn JH (1968) The development of the adrenergic fibre. Br J Pharmacol 32:575-582 Burn JH (1969) Essential pharmacology. Annu Rev Pharmacol 9:1-20 Burn JH (1971) Release of noradrenaline from sympathetic endings. Nature 231: 237 -240 Burn JI-I (1976) The discovery of uptake of adrenaline in 1930-1933 and the development of the adrenergic fibre from a cholinergic fibre. J Pharm Pharmacol 28: 342-347 Burn JH (1977) Evidence that acetylcholine releases noradrenaline in the sympathetic fibre. J Pharm Pharmacol 29:325-329

MARTHE VOGT

Agricultural Research Council Institute of Animal Physiology Babraham Cambridge CB2 4AT, U.K. Rev. Physiol. Biochem. Pharmacol., Vol. 94 © by Springer Verlag 1982

Cardiovascular Sympathetic Afferent Fibers

ALBERTO MALLIANI*

Contents 1. Introduction ...... 11 2 Terms and History ...... 12 3 Morphology ...... 14 4 Methodology ...... 15 5 Functional Characteristics of the Various Types of Cardiovascular Sympathetic Afferent Fibers ...... 18 5.1 Atrial Receptors ...... 20 5.2 Ventricular Receptors ...... 23 5.3 Coronary Receptors ...... 35 5.4 Receptors in the Large Thoracic Vessels ...... 36 5.4.1 Aorta ...... 36 5.4.2 Pulmonary Artery ...... 40 5.4.3 Pulmonary Veins ...... 41 6 Reflexes Mediated by Sympathetic Afferent Fibers ...... 42 6.1 Acute Experiments ...... 43 6.2 Chronic Experiments ...... 51 7 The Positive Feedback Hypothesis ...... 58 8 General Properties of Cardiovascular Sympathetic Afferent Fibers: A Summary ...... 61 9 Human Pathophysiology ...... 63 References ...... 66

1 Introduction

In 1976, an important symposium on Cardiac Receptors was held in Leeds (Hainsworth et al. 1979). One of the topics was entitled Electrophysiology and Reflexes of "'Sympathetic" Afferents. For the first time the term "sympathetic" was officially used to describe the afferent nerve fibers running in the sympathetic nerves. However, as indicated by the quotation marks, some uncertainty still existed. On that occasion I expressed the view that the new experimental data justified the use of this term

* Istituto Ricerche Cardiovascolari, CNR, Fondazione I. Monzino; and Patologia Medica, Ospedale "L. Sacco"; University of Milan, Italy. Address correspondence to: Istituto Ricerche Cardiovascolari, Via Bonfadini 214, 20138 Milano, Italy. 12 A. Malliani

(Malliani 1979). As a matter of fact, after that symposium the cardiovascular sympathetic afferent fibers became more widely accepted as part of the neural afferent pathways that participate in the regulation of the cardiovascular functions. This review may seem premature. However, its main justification is that some concepts related to new findings may have general implications, and it does not attempt to draw simple conclusions from such new evidence. The aim of this review is to discuss three hypotheses that, I think, have adequate supporting data: 1. A similar organization characterizes the basic neural mechanisms of the somatic and visceral nervous systems: an organization that can be defined as Sherringtonian and that recognizes the fundamental role of the reflex arc. 2. Cardiovascular sympathetic afferent fibers mediate reflexes that are mainly excitatory and exhibit positive feedback characteristics. 3. The nociceptive function, considered for a long time as the unique property of these fibers, seems to be based, mainly if not exclusively, on their intense activation rather than on the recruitment of specific cardiovascular nociceptors.

2 Terms and History

Edgeworth (1892) first suggested the existence of afferent nerve fibers in the cardiac sympathetic nerves which he called "sympathetic sensory fibres." Langley (1903) also sporadically wrote about "afferent sympathetic fibres" but eventually rejected the expression with his definition of the autonomic nervous system being pure outflow. It is well known that, following Professor Jebb's suggestion, Langley (1898) coined the term autonomic, indicating that the structures supplied by the system are not subject to voluntary control but operate to a large extent independently. The afferent fibers in the sympathetic nerves were considered "somatic", because they had their cell bodies in the dorsal spinal ganglia together with somatic neurons, because they were thought to have no reflex role, and because their functions were assumed to be exclusively nociceptive (Langley 1903). Visceral pain also gave rise to much discussion, "the pain of visceral and somatic disease" being attributed, even several decades later, to "direct stimulation of a common system of pain nerves" (Lewis and Kellgren 1939-1942). In short, during the same years that witnessed Sherrington's enlighten- ing experiments leading to the coexisting concepts of "proprioceptive reflex" and "dominance of the brain" (1898, 1906), the visceral reflex Cardiovascular Sympathetic Afferent Fibers 13 spinal arc was considered either an oversimplification devoid of any functional significance or a basically wrong concept. That was only the beginning: in the years that followed, it was generally agreed that only the cardiovascular the afferent autonomic fibres to those which end in tissues which receive reflexogenic areas (Heymans and Nell 1958). However, Langley, who was known for "intimating" his opinions (see Ranson and Billingsley 1918a, p. 422), must have had more doubts on "sympathetic" afferent fibers than we think. He said, "We might, however, restrict the afferent autonomic fibres to those which end in tissues which receive efferent autonomic fibres, i.e. in mammals to the afferent fibres of unstriated muscle, cardiac muscle and glands..." and "all that seems to me possible at present towards arranging afferent fibres into autonomic and somatic divisions is to consider as afferent autonomic fibres those which give rise to reflexes in autonomic tissues, and which are incapable of directly giving rise to sensation; and to consider all other afferent fibres as somatic" (Langley 1903). The crucial fact was that Langley could only count on negative experiments: "Such fibres ought when stimulated to produce reflexes of one sort or another even though slight. But in experiments made earlier I could not find with certainty reflex action of any kind..." (1896). In short, I would like to suggest that it is likely that Langley had a more open mind on this topic than is generally believed. The term "sympathetic" afferent fibers has been proposed recently (Malliani et al. 1973b, 1975a) for several reasons which include simplicity and analogy with vagal afferent fibers. It is not simply a problem of terminology but a point essential to the concept that the visceral nervous system may have its basic functional unit in the spinal reflex arc: "The reflex arc is the unit mechanism of the nervous system when that system is regarded in its integrative function" (Sherrington 1906). Accordingly, the sympathetic input to the spinal cord may be as important to the regulation of the sympathetic outflow as the somatic spinal input is to the regulation of the somatic nervous outflow (Malliani et al. 1975a). In conclusion, the term reflects the original Winslow definition of sympathetic nerves as an ensemble of nerves "bringing about the sympathies of the body" (quoted by Langley 1915-1916), stresses their composite nature of efferent and afferent fibers, underlines the new experimental findings on sympatho-sympathetic reflexes (Malliani et al. 1975a), and is econom- ical in the use of words in comparison with expressions such as "afferent nerve fibers running into the sympathetic nerves." 14 A. MaUiani

3 Morphology

Many anatomical studies have been carried out, over almost a century, on the sensory innervation of the heart, and yet, we have to admit that our knowledge is still remarkably scanty. There are many reasons that can justify the elusive results of so much work and a brief explanation of some of these difficulties will provide the most realistic introduction. 1. The heart possesses a double sensory innervation of afferent nerve fibers running in the vagi or in the sympathetic nerves: therefore, with the histological techniques in use until now, vagal and sympathetic endings can only be discriminated on the basis of selective degeneration studies. 2. As methods for specific staining of afferent neurons and their receptive endings are not available, the attribution of a sensory function to a morphological finding often, if not always, bears some uncertainty. 3. Such uncertainty may even become presumption in the case of electron microscopy. On the other hand, this is the only technique available that can adequately identify terminal endings (Tranum-Jensen 1975). 4. Finally, a minor difficulty is the fact that all staining techniques suffer from variability: they oscillate from a too generous visualization of neural and non-neural elements to an incomprehensible selection of only a few neural elements. In more general terms, moreover, it is known that even though a morphological clear cardiac sensory ending can be identified, we have no information on where the graded electrogenesis of the generator potential occurs and on where propagated activity is initiated. The existence of sensory endings in the heart was first suggested by Berkeley (1894), Smirnow (1895) and Dogiel (1898). But Edgeworth (1892), following Gaskell's suggestion, was the first to describe large nerve fibers in the cardiac sympathetic nerves: fibers that he traced to the heart and that he considered to be sensory in function. It is remarkable that Gaskell (1886) had already recognized in the sympathetic white rami the presence of nonmyelinated fibers arising from the posterior root ganglia: however, he probably interpreted them as the efferent axons of autonomic cells contained in the spinal ganglia. Thirty years later, Ranson and Billingsley (1918b) indicated the sensory nature of these nonmyelinated fibers. In short, early anatomical studies suggested that the sympathetic sensory supply of the heart was made up of both myelinated and nonmyelinated afferent nerve fibers. Recent anatomical studies have confirmed the existence of both types of afferent fibers in the cardiac sympathetic innervation (Coggeshall and Galbraith 1978; OldfieM and McLach- lan 1978;Seagard et al. 1978). Cardiovascular Sympathetic Afferent Fibers 15

In the heart, the sensory fibers terminate as complex, unencapsulated endings that are usually distinguished as either diffuse or compact (Noni- dez 1939;Miller and Kasahara 1964). It is still an unanswered question whether an "'end-net" or "terminal reticulum" (Meyling 1953 ; Mitchell 1953 ; Holmes 1957a, b; Khabarova 1963; Miller and Kasahara 1964; Williams 1964; Johnston 1968)truly exists or is rather the result of structural artifacts of impregnation (Botdr 1966; Floyd 1979). Some authors attributed a sensory function to such an end-net formation (Miller and Kasahara 1964; Williams 1964). Practically all types of nerve endings have been described in the sub- endocardial tissues, but different nerve terminals likely to be sensory seem also to exist in the depth of the myocardium (Khabarova 1963) and around the coronary vessels (Nettleship 1936). Concerning the contribution of vagal or sympathetic fibers to these sensory endings within the heart, Wollard (1926) concluded that a large proportion of cardiac sensory endings were of vagal origin: indeed he observed that an experimental bilateral stellectomy did not markedly modify what he considered to be the normal aspect of the sensory supply of the heart. Nonidez (1939) also believed that the majority of cardiac sensory fibers joined the vagi. The conclusions reached by Nettleship (1936) are more precise: the removal of the dorsal ganglia produced degeneration of fibers in the endocardial net at the apex of the ventricles and from the walls of the coronary vessels. More recently Holmes (1957a)observed survival of the "terminal nervous network" after vagotomy: if this structure were really sensory, the sympathetic afferent fibers are likely to be implicated. Recent literature has not contributed further to a solution: the most valuable degeneration studies are still to be found in the earliest papers. As a working hypothesis, we may, however, accept Khabarova's (1963) statement that "afferent fibers of spinal type innervate the same regions and layers of the heart as the vagal fibers, and their afferent fibers and endings frequently lie side by side with afferent fibers and endings of the vagus nerves". This opinion has the merit that it agrees with the electrophysiological findings which, so far, have suggested that vagal and sympathetic sensory endings are intermingled in all regions of the heart.

4 Methodology

Afferent sympathetic nerve fibers with receptor endings in the heart or in the great thoracic vessels can be isolated, for electrophysiological recordings, from three different points: a) the cardiac sympathetic nerves, 16 A. Malliani

b) the rami communicantes, c) the spinal dorsal roots. For proper interpretation of these experimental findings one must be aware of the ad- vantages and limitations of each approach. a) The impulse activity that can be recorded from the cut peripheral end of a cardiac sympathetic nerve (Brown and Malliani 1971;Armour 1973) is largely afferent in nature although active efferent fibers may also be present. Moreover, as many vagal axons are present in the cardiac sympathetic nerves (Noniclez 1939) there is no way of ascertaining whether individual fibers are sympathetic or vagal. Therefore, this approach is likely to furnish equivocal data, unless each finding is corroborated by similar ones obtained by the other approaches (Brown and Malliani 1971). b) A recording from the cut peripheral end of a ramus communicans (Fig. 1) can conclusively identify impulse activity directed to the spinal cord. However, the rami communicantes also contain a variable number of sympathetic postganglionic efferent fibers, largely predominant in the grey ramus, but also present in the white ramus (Ranson and Billingsley

injection

ganglion

ubcl. _J--L_ r "-n_.r-- vena cava T3 T pump

common i I iac a. -_-_-_=:: Fig. 1. Schema of the experimental model used in the cat for recording impulse activity of single afferent ventricular sympathetic nonmyelinated nerve fibers (Lombardi et al. 1981b). The left main coronary artery is perfused according to the method of Brown (1968). The conduction velocity of the recorded fiber is determined by stimulating the inferor cardiac nerve (ICN) or the surrounding tissues (Malliani et al. 1973b; Malliani and Pagani 1976; Casati et al. 1979). The extracorporeal perfusion circuit allows the interruption of the left main coronary artery flow or the intracoronary administration of chemical substances without direct manipulation of the heart (Lombar- di et al. 1981b) Cardiovascular Sympathetic Afferent Fibers 17

1918a, b). Somatic afferent fibers mainly from the neck muscles also run through the high thoracic rami communcantes (Mizeres 1955;Holmes and Torrance 1959). Therefore, recordings from the rami can be soundly interpreted only if functionally isolated afferent' fibers are studied yielding action potentials constant for shape and amplitude, and if the sensory fields initiating the impulse activity can be located with appropriate maneuvers. In the case of cardiovascular mechanoreceptors the only location of the receptor endings that can be considered entirely sound is that obtained post mortem in the absence of circulation by using discrete mechanical probing (Coleridge et al. 1957). It is clear that the main danger implicit in the interpretation of recordings from the cut peripheral end of rami communicantes is to attribute to afferent sympathetic fibers action potentials which are derived from postganglionic efferent fibers running centripetally through the rami. An additional and important positive aspect of this approach is that only minor though skilled surgery is necessary to reach the rami, hence recordings can be obtained in animals under apparently normal hemodynamic conditions and, if necessary, also with a closed chest (Malliani et al. 1975a). c) The isolation of sympathetic afferent fibers from the dorsal roots should not be affected by efferent impulse activity. However major surgery is needed and the afferent fibers possibly reaching the spinal cord through the ventral roots (Coggeshall et al. 1974; Coggeshall 1980) would be missed. In conclusion, only afferent nerve fibers with cardiovascular receptor endings isolated from the rami communicantes or from the dorsal roots, but running through the sympathetic nerves, can be safely defined as cardiovascular sympathetic afferent fibers (Malliani 1979; Malliani et al. 1973b, 1975a). As to identification, in the course of electrophysiological experiments, of afferent nerve fibers as myelinated or nonmyelinated, it must be recalled that the distinction is based on a purely functional criterion consisting of a nerve conduction velocity above or below the generally accepted frontier of 2 m/s (Burgess and Perl 1973). Obviously such a criterion should not be regarded as absolute: for instance, the conduction velocity of a fiber can be decreased by factors such as low temperature and various types of mechanical and chemical damage. 18 A. Malliani

5 Functional Characteristics of the Various Types of Cardiovascular Sympathetic Afferent Fibers

In the anesthetized animal under resting hemodynamic conditions, the spontaneous impulse activity of sympathetic afferent fibers with endings in the heart or in the large thoracic vessels has one feature that seems independent of the location of the receptive field: it usually consists of, at most, one action potential per cardiac cycle, each cycle being not neces- sarily accompanied by a nervous impulse. If this observation, which we have repeatedly made (Malliani et al. 1972b, 1973b, 1975a;Malliani and Pagani 1976; Casati et al. 1979;Malliani 1979; Lombardi et al. 1981b), is accepted, it follows that when multiple impulses per cardiac cycle are present in the resting state they may belong to a multifiber recording, to other types of nerve fibers such as vagal afferent fibers (Armour 1973), or to a fiber whose endings have been damaged in the course of the experiment, e.g. by mechanical manipulations. However, changes in hemodynamic conditions induce repetitive firing during each cardiac cycle (see below). The temporal relation between the action potentials and a particular hemodynamic event is likely to be determined by the location of the sensory endings. However, while such a temporal correlation is almost always detectable in the discharge of myelinated afferent fibers, it is rarely apparent in the background impulse activity of nonmyelinated afferent fibers (Malliani et al. 1973b;Nishi et al. 1974; Uchida et al. 1974; Uchida 1975a; Malliani and Pagani 1976; Casati et al. 1979). To conclude these preliminary comments it is useful to recall the investigators who made the first observations. Beccari (1934) obtained from the vertebral nerve a few recordings that possibly included the activity of sympathetic afferent fibers and that oc- casionally displayed a cardiac rhythm, a characteristic that, however, does not prove the cardiovascular location of the receptors. Those experiments remained, however, quite isolated. The favorable anatomical location of the vagi in the neck compared with the intrathoracic seclusion of the cardiac sympathetic nerves is likely to have influenced, for many years, the choice of vagal afferent fibers for the electrophysiological attempts to record impulses from cardiovascular receptors. In addition, the intensity of afferent impulse traffic present in cardiovascular vagal afferent fibers was obviously more rewarding compared with the sparse activity detected from the peripheral cut end of a sympathetic nerve. Yet, concepts more than facts probably represented the true obstacle: in particular the concept that cardiovascular sympathetic afferent fibers had no physiological regulatory function. Cardiovascular Sympathetic Afferent Fibers 19

The first systematic attempt to investigate the properties of thoracic sympathetic afferent fibers can be found in the study by Holmes and Torrance (1959): a remarkable paper stimulated, however, more by an anatomical culture than by new physiological considerations. Most of the afferent fibers studied by these authors had no spontaneous discharge and innervated thoracic structures other than the heart and large vessels; an impulse activity phasic with cardiac rhythm was sporadically noticed and interpreted as coming from receptor endings located near the blood vessels. Brown, in his Ph.D. thesis (1964) first reported recordings from cardiac sympathetic afferent fibers, most of which had no spontaneous discharge and which could be activated by mechanical or chemical stimuli. Subsequently (Brown 1967) this afferent sympathetic activity was interpreted as bearing only pathophysiological significance inthe transmission of cardiac pain, as it was very low in baseline conditions and highly excited during myocardial ischemia. Ueda et al. (1969) carried out the first detailed electrophysiological study of the impulse activity of cardiovascular sympathetic afferent fibers. The fibers were found to be responsive both to mechanical probing and to hemodynamic stimuli: however, these findings were again interpreted only as an evidence that cardiac pain could be elicited mechanically. The demonstration that in spinal vagotomized animals increases in arterial blood pressure, sometimes of moderate magnitude, could elicit sympatho-sympathetic reflexes (Malliani et al. 1970, 1971a) was crucial for the new hypothesis that cardiovascular sympathetic afferent fibers could be tonically involved in the neural regulation of the circulation and body fluids. Indeed, cardiovascular sympathetic afferent fibers were found to display a spontaneous impulse activity related to normal hemodynamic events (Malliani et al. 1972b, 1973b).

Location of the Receptors.This fundamental point can be explored only generally by electrophysiological experiments. In the case of mechanoreceptors, discrete mechanical probing is usually considered adequate although it has several important limitations. For instance, it produces a tissue deformation that bears little resemblance to the natural events which normally excite the receptors; thus the preterminal regions or even the fibers en passage (Catton 1970) may be activated. Hence, there is the possibility that mechanical probing may activate various regions simply possessed of an electrogenically reactive membrane (Grundfest 1966) without identifying the area normally responsible for triggering the action potentials. At the time of our first experiments on cardiovascular sympathetic afferent fibers we preferred a "functional localization mainly because in 20 A. Malliani

our hands a procedure such as probing the heart (most often performed while the heart was beating) never gave satisfactory results, since afferent fibres were often activated by probing more than one spot" (Malliani et al. 1971b). Indeed, mechanical probing of nearby regions, carried out in the presence of circulatory pulsations and respiratory movements, can activate from a distance a sensory field. This can be erroneously interpreted as evidence of a multiterminal afferent nerve fiber. Another common course of error arises from recordings of poorly distinguishable action potentials belonging to a multifiber preparation and erroneously said to be derived from a single axons. However, it has also been adequately demonstrated that both in the presence and absence of a circulation and following the methods described by Coleridge et al. (1957), cardiovascular sympathetic afferent fibers can be excited by probing several distinct spot-like areas (Coleridge et al. 1975, 1978; Malliani and Pagani 1976) (see below). In all our subsequent experiments we have studied no more than one fiber per animal (with a few exceptions in which a recording was obtained containing two different types of action potentials of constant and clearly identifiable shape, as in Figs. 9 and 10): for each fiber the sensory field or fields were identified post mortem. It should be pointed out that only very light preliminary probing should be used for locating receptive fields, after having identified functionally the location of the receptor and preferably after having already studied its functional characteristics. In fact, an abundant and blind probing may damage fibers or their endings, especially if they are nonmyelinated, and with possible consequences such as decreased sensitivity to the stimuli, an abnormal spontaneous discharge, bursting activity, etc. It will become clear that the data from the various laboratories have not always been collected in comparable ways.

5.1 Atrial Receptors

Afferent sympathetic nerve fibers with their receptive endings located in the atrial walls have been described in numerous reports. The nerve fibers were myelinated (Malliani et al. 1973b; Uchida and Murao 1974c; Uchida 1975a) or nonmyelinated (Uchida and Murao 1974c; Uchida 1975a) as inferred from their conduction velocities. In the experience of one laboratory (Malliani et al. 1973b; Malliani 1979) all atrial mechanoreceptors had a spontaneous impulse activity, while a second laboratory (Ueda et al. 1969; Uchida and Murao 1974c; Uchida 1975a) rarely observed a spontaneous discharge. Nonmyelinated fibers were more frequently silent and could be activated by mechanical stimuli or chemical substances, such as Cardiovascular Sympathetic Afferent Fibers 21 potassium chloride or bradykinin applied topically to the epicardial surface. Within the spontaneous impulse activity there was a temporal relation between the action potential and a particular intra-atrial pressure wave (Malliani et al. 1973b, 1975a; Uchida and Murao 1974c;Malliani 1979) (Fig. 2). Fibers were found to discharge in phase with atrial systole (a wave of the atrial pressure) (Figs. 2a, 3a), with bulging of the atrio-ventricular valves (c wave) (Fig. 2b), and with atrial filling (v wave) (Fig. 2c). For some fibers a particular phasic pattern of spontaneous discharge was constant for periods of hours. However, such patterns could also change spontaneously (MaUiani et al. 1973b;Malliani 1979) (Fig. 2d, e). These observations were all obtained in artificially ventilated animals with the chest opened. However, a similar activity from atrial mechanoreceptors could also be recorded in animals with closed chest, breathing spontaneously. Opening the thorax and the pericardium did not grossly modify the firing of the fibers whose endings were found, post mortem, to be in the atria (Malliani et al. 1973b, 1975a).

2OO m m..0] .... [: m H2O

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[

1 s Fig. 2a--e. Spontaneous impulse activity of fibers with right atrial endings. Each record shows the activity of a different fiber, except a and d, which illustrate the discharge of the same fiber. Tracings, from top to bottom, represent the arterial blood pressure, the right atrial pressure, the ECG and the action potentials. (From Malliani et al. 1972b, unpublished work) 22 A. Malliani

mm Hg 1" t ~©,. HzO :t~ "1 ~-30 ] r o ~~L e ------~--~-- - ~-L

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1~. 1 s Fig. 3a--f. Activity of a fiber with right atrial endings during hemodynamic stimuii. The upper tracing represents the endotracheal pressure (inflation upwards); the other tracings as in Fig. 2. a Spontaneous impulse activity; b mechanical probing of an area of the right atrium, performed on the beating heart; c constriction of the pulmonary artery; d after rapid bleeding (30 ml in about 3 min); e reinjection of blood; f last part of the reinjection of blood. (From Malliani et al. 1975a)

The discharge of afferent cardiac sympathetic fibers with atrial endings was increased during rises in atrial pressure however obtained (Malliani et al. 1973b; Uchicla andMurao 1974c; Uchida 1975a; Kostreva et al. 1975). Examples are shown in Fig. 3, illustrating the impulse activity of a right atrial receptor that spontaneously discharged in phase with atrial systole (Fig. 3a). A preliminary mechanical probing of an area of the right atrium, performed while the heart was beating, is illustrated in Fig. 3b. The fiber was excited during an increase in right atrial pressure obtained with the constriction of the pulmonary artery (Fig. 3c) or with reinjection of blood (Fig. 3e, f). Conversely, the impulse activity of atrial mechanoreceptors was always reduced or even abolished during reductions in atrial pressure as obtained while bleeding the animal (Fig. 3d) (Malliani et al. 1973b). Atrial receptors can also be excited by chemical substances (Uchida and Murao 1974c; Nishi et al. 1977): this "polymodal" (Burgess and Perl 1973) sensitivity and the possible existence of purely chemosensitive endings will be discussed together with the more numerous data concerning left ventricular receptors (see below). On the basis of our knowledge it seems impossible to identify the mechanical event that mainly regulates the activity of atrial mechanoreceptors. As their discharge can occur spontaneously during either atrial Cardiovascular Sympathetic Afferent Fibers 23 systole or diastole, it seems likely that they can be excited by both muscular contraction and stretch. Comparison of the spontaneous activity of these afferent sympathetic fibers and that of the similarly myelinated afferent vagal fibers with atrial endings shows that the most obvious difference is that vagal fibers usually yield bursts of impulses during each cardiac cycle as opposed to a single impulse. This limits the possibilities of investigating the "static" and "dynamic" components of the transducing properties of the atrial sympathetic receptors that so far have not been studied with approaches similar to those used for atrial vagal receptors (Recordati et al. 1975, 1976).

5.2 Ventricular Receptors

With Myelinated Nerve Fibers. Different groups of researchers agree that ventricular sympathetic receptors with myelinated nerve fibers possess a mechanosensitivity which is the cause, in normal hemodynamic conditions, of their spontaneous impulse activity (Malliani et al. 1973b, 1975a; Hess et al. 1974; Uehida et al. 1974; Uehida 1975a). In the experience of one group of workers (Malliani et al. 1973b, 1975a) this background discharge consisted of, at most, one action potential per cardiac cycle, usually following the onset of the Q waves of the ECG by 40-120 ms (Figs. 4, 5a). For most fibers, not all cardiac cycles were accompanied by an action potential; therefore, the discharge was irregular although a cardiac periodicity was detectable. A regular discharge was infrequent (Fig. 4). ECG~ AP~ ~~-mmHg ~150 " - " "~90 dP~ddt ..~ ~,'~(~~ ~ ~ h~L ~ ~~ ~ ~ I+0300nH~s~ ~-3000 150 LVP~'~ j(~~~f~/t'~ (~~'~f~~j~ fom Hg

I ] rl .... r rI'J p 'l rl l"r'~' -

, 0.5 , 1S i i Fig. 4. Spontaneous impulse activity of a myelinated nerve fiber with left ventricular endings. Tracings, from top to bottom, represent the ECG, the arterial blood pressure, the left ventricular dP/dt, the left ventricular pressure, and action potentials 24 A. Malliani 2oo-]~ mm Hg ~ 30 oJ [O c m H20 I _ l _ i . I - I I . I I I I i . I I _ I i

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¢ 1 S i Fig. 5a-c. Implalse activity of a fiber with right ventricular endings. Tracings as in Fig. 3. a Spontaneous impulse activity; b after bleeding 10 ml blood, which abolished the discharge of the fiber, a fast reinjection of blood begins at the arrow (note that the first action potential occurs during a diastole); c mechanical probing of an area of the right ventricle, performed on the beating heart. (From Malliani et al. 1973b, unpublished work)

The coincidence between spontaneous action potentials and ventricular contractions is a general finding (Ueda et al. 1969; Hess et al. 1974; Uchida et al. 1974; Nishi et al. 1977); however, receptors firing spontaneously during ventricular diastole have also been noticed (Ueda et al. 1969; Uchida et al. 1974). Ventricular receptor endings were excited during increases in ventricular pressure (Ueda et al. 1969;Malliani et al. 1973b; Uchida 1975a;Nishi et al. 1977) and, conversely, their discharge decreased during reductions in ventricular pressure (Malliani et al. 1973b; Uchida 1975a). Figure 5 illustrates the impulse activity of a right ventricular receptor: the discharge was abolished by a moderate bleeding of the animal, restored, and excited by fast restitution of blood (Fig. 5b). These ventricular endings can also be excited by chemical substances such as bradykinin (Uchida and Murao 1974d; Nishi et al. 1977), veratridine (Malliani et al. 1973b, 1975a;Nishi et al. 1977), and acids (Uchida and Murao 1975). This responsiveness as well as the behavior of ventricular receptors during reductions in coronary flow will be discussed together with the response of ventricular nonmyelinated afferent fibers. Cardiovascular Sympathetic Afferent Fibers 25

a b

L2 200

I r f - -- r '' " '

0.5 S J

Fig. 6a, b. Impulse activity of an afferent sympathetic nonmyelinated nerve fiber with its receptive field in the left ventricle. Tracings represent from top to bottom, the ECG, the systemic arterial pressure, the left ventricular pressure and neural activity. a Spontaneous activity; b during occlusion of the aorta. The fiber conduction velocity was 0.87 m/s; the measured conduction distance from the receptive field to the recording electrode was 9.6 cm. Dots indicate the approximate relation between impulses and cardiac cycles, taking into account a conduction time of 110 ms. (From Casati et al. 1979)

With Nonmyelinated Nerve Fibers. A fixed temporal correlation between receptor impulses and ventricular dynamics is most often not detectable (Uchida et al. 1974; Uchida 1975a; Casati et al. 1979; Lombardi et al. 1981 b); a clear difference from the discharge of myelinated sympathetic ventricular afferent fibers. However, in some cases, after taking into account the conduction time within the fiber, most of the spontaneous impulses appear to occur during ventricular systole (Fig. 6) (Casati et al. 1979). In a recent study (Casati et al. 1979) several hemodynamic stimuli were used in order to determine the functional properties of these receptors. As shown in Fig. 7, the impulse activity of all tested fibers was significantly increased when ventricular pressure was elevated by mechanical obstructions of the thoracic aorta, during positive inotropic interventions induced by i.v. injection of isoprenaline (0.2/~g/kg) or during rises of left ventricular end-diastolic pressure produced by i.v. infusion of isotonic NaC1. Conversely, acute reductions in venous return produced by the occlusion of the inferior vena cava decreased the receptor firing that was unmodified during bleeding of the animal. In short, these sympathetic receptors would be responsive to both ventricular contraction and distension. Some examples of these responses are illustrated in Fig. 8. 26 A. Malliani imp/s 3 ~¢

AO Isopr. Inf. LCO IVCO Bleed. Ach. Asph. VF n: 28 ii19 18 10 12 23 19 7 26 control ~ stimulus

Fig. 7. Responses of ventricular sympathetic nonmyelinated afferent fibers to the interventions. A O aortic occlusion; Isopr. i.v. injection of isoprenaline; Inf i.v. infusion of isotonic solution; LCO left coronary occlusion; IVCO inferior vena cava occlusion; Bleed bleeding; ACh i.v. injection of acetylcholine; Asph. asphyxia; VF ventricular fibrillation; n number of fibers studied; ***P < 0.001 ; **P < 0.02; n.s. not statistically significant. (From Casati et al. 1979)

During the excitation elicited by aortic occlusion (Fig. 8a), the impulses, if one considered the conduction time, occurred 60-70 ms after the beginning of the ventricular complex of the electrocardiogram: it should also be noticed that the impulse frequency of the fiber was higher during the rising phase of the stimulus than during its plateau. This would indicate a "dynamic" and "static" component in the response of the receptor (Burgess and Perl 1973). It is interesting that all ventricular sympathetic receptors with nonmyelinated fibers were excited during ventricular fibrillation. Various patterns were noticed. In some cases, the ventricular receptors were immediately and strongly excited; for example, frequency of discharge increased in the bursts up to 47 imp/s (Fig. 9c) at the beginning of the fibrillation episode. More frequently, excitation was continuous during the whole fibrillation episode, however without bursts of high frequency discharges (Fig. 10c, d). The excitation appeared after a mean latency of about 10 s. This excitation of ventricular receptors during ventricular fibrillation was likely to reflect a mechanical stimulation in those cases in which a precise temporal correlation existed between onset of fibrillatory movements and sudden enhancement of the frequency of the impulses (Fig. 9c). However, this does not rule out that in the course of the episode some chemical substance may contribute to the depolarization of the endings. Such as mechanism would be compatible with those cases in which some Cardiovascular Sympathetic Afferent Fibers 27

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Fig. 8a-e. Activity of an afferent sympathetic nonmyelinated nerve fiber with its receptive field located in the left ventricle. Tracings represented from top to bottom, the ECG, the systemic arterial pressure, the right atrial pressure, the nervous activity (all tracings are cathode-ray oscilloscope recordings), a Occlusion of the descending thoracic aorta (indicated by the rise in arterial pressure); b i.v. injection of 5 ml warm saline, beginning at the arrow; c occlusion of the inferior vena cava released at the arrow; d electrical stimulation of the left inferior cardiac nerve activating the afferent fiber; the biphasic first deflexion is the artifact of the stimulus, detectable also on the ECG trace, while the second biphasic deflexion is the action potential of the fiber. The approximate length of the fiber was 3.8 cm. The conduction velocity calculated for this fiber was 0.92 m/s; e mechanical probing of an area of the external surface of the left ventricle, performed on the non-beating heart, after bleeding the animal to death; notice the after-discharge which is typical of group C fibers. (From Casati et al. 1979) seconds elapsed before normal firing was restored after the fibrillation had subsided (Fig. 9d). In five instances, the activity of one nonmyelinated and one myelinated nerve fiber with left ventricular endings were recorded simultaneously from the same nerve strand during episodes of ventricular fibrillation: three myelinated ventricular afferent fibers were excited (Fig. 10c, d), while the other two seemed to be unaffected. Although these data are 28 A. Malliani a b mmHgJ [ ~20 ° l [om'20

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Fig. 9a-d. Activity of a nerve filament containing impulses of two different nonmyelinated fibers: the fiber yielding biphasic action potentials had its receptive field in the depth of the left ventricle, while the receptive field of the fiber with monophasic potentials was in the left atrium. Tracings as in Fig. 8. a Occlusion of the descending thoracic aorta; b electrical stimulation of the left inferior cardiac nerve activating both afferent fibers; the biphasic first deflection is the artifact of the stimulus, followed by a double activation of the atrial fiber and by the potential of the ventricular fiber. The approximate length of the fiber was 4.8 cm. The conduction velocity calculated for the ventricular and atrial fibers was respectively 0.32 m/s and 0.53 mJs; c an episode of ventricular fibrillation is induced by gentle mechanical stimulation of the right ventricle, corresponding to the ectopic beat preceding the episode itself by a few cardiac cycles; d the ventricles spontaneously return to a normal action after about 80 s. (From Casati et al. 1979;in part unpublished work) insufficient to draw any quantitative conclusion on the behavior of myelinated ventricular afferent fibers during ventricular fibrillation, these results indicate that there are circumstances in which the endings of myelinated and nonmyelinated fibers appear to be influenced in a different manner by the same local event. In their responses to acute bleeding, myelinated and nonmyelinated ventricular afferent fibers also behaved differently. The latter did not reduce their discharge (Fig. 7): more abrupt reductions in venous return were needed, such as those obtained with the occlusion of the inferior vena cava (Figs. 7, 8c), in order to reduce activity. Cardiovascular Sympathetic Afferent Fibers 29

a b

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Fig. 10a-d. Sympathetic nerve filament containing a nonmyelinated and a myelinated afferent fiber, both with their receptive field in the left ventricle. The action potentials of the nonmyelinated fibers are marked with dots; the largest potentials were produced by the myelinated fiber. Tracings as in Fig. 8. a Occlusion of the descending thoracic aorta; b electrical stimulation of the inferior cardiac nerve; the stimulus artifact cor- responds to the first deflexion indicated by the arrow; the large action potential of the myefinated fiber is barely distinguishable from the artifact, followed after a long latency by the potential of the nonmyelinated fiber. The approximate length of the nerve was 5.6 cm. The calculated conduction velocity was 0.36 m/s for the nonmyelinated and 7.23 m/s for the myelinated fiber, c Ventricular fibrillation is induced by a high-frequency electrical stimulation of the right ventricle; d spontaneous interruption of the fibrillation episode after 68 s. (From Casati et al. 1979; in part unpub- fished work)

For most atrial and ventricular afferent fibers only one sensory field was found on probing the heart, post mortem. However, in a few cases, afferent fibers were excited equally from two distinct but nearby areas (Malliani et al. 1973b; Nishi et al. 1977). The finding of multiple sensory cardiac fields was more frequent in the experiments by Coleridge and associates (Coleridge et al. 1975, 1978; Baker et al. 1980). I can provide no explanation for this quantitative difference as the mechanical probing was also often performed post mortem by these authors (however, they did not study only one fiber per experiment). A similar observation of multiple sensory fields was first made on afferent vagal fibers with epicardial receptors by Sleight and Widdicombe (1965). 30 A. Malliani

Finally, it should be stressed that some ventricular endings could only be excited by a probing performed against the internal surface of the opened ventricle or by mechanical stimuli deforming the depth of the ventricular muscle, e.g. punctures with penetrating needles (Malliani et al.

a -1 ...... ; I,_ ~, , L ..... J ..... I

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[

~E [ I..Jllll,.1:_ LLil [ .... I...L .ll.l A ,,L..:,. h, I ,,,.J..l~

Fig. lla-f. Effects of a prolonged interruption of left coronary arterial flow. Fiber with right ventricular endings. Tracings represent, from top to bottom, the coronary inflow pressure, the arterial blood pressure, the right atrial pressure, the ECG, the nervous recording (cathode-ray oscilloscope recordings), a Control (the flow is set at 11 ml/min); b the record starts 70 s after the coronary perfusion has been interrupted; c starts 39 s after the end of the preceding record; d after additional 67 s; a coarse ventricular fibrillation is present. Fifteen seconds after the end of d the coronary perfusion is instituted again, however, the ventricles do not contract; e 10 s later cardiac massages are performed (markedly exciting, mechanically, the endings of the fiber); f progressively the heart recovers (e and f are continuous tracings), (From Malliani et al. 1973b) Cardiovascular Sympathetic Afferent Fibers 31

1973b; Casati et al. 1979). In these cases a probing performed on the beating heart would be ineffective in identifying the mechanosensitive endings.

Effects of Reduction in Coronary Flow. In order to interpret correctly the effects of reduction in coronary flow on the activity of cardiac receptors, it is crucial to avoid undue direct mechanical stimulation of the fibers en passage or of their receptor endings. To this purpose, coronary perfusion can be used (Fig. 1) and myocardial ischemia can be produced by interrupting the action of the perfusion pump without manipulation of the heart (Brown and Malliani 1971 ;Malliani et al. 1973b; Lombardi et al. 1981b). Alternatively, the pericoronary nerves can be surgically isolated

8 200~ mmHg] ~-2QO I ' I J I I [ I ltll!!!!!!!![!!![[![t"H!!!!!!!!!!!!!!!',!!![!![[[[[![[!" b

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...... i _I_ ...... !] li ,l aa,~,n,]!,,!,l!il,iH!,!10,,I,LLII,I,i,,]!] I [ I1' L - i-- [ -- . rt i i ~mlltt~lHllllrEIT{hH;ll. nl11;l[]l]Hrl; 1 S ,2s

Fig. 12a-f. Activity of an afferent sympathetic nonmyelinated nerve fiber with a left ventricular sensory field. Tracings represent, from top to bottom, systemic arterial pressure, coronary perfusion pressure, nerve impulse activity (cathode-ray oscilloscope recordings), a Interruption of the left main coronary artery perfusion; b intracoronary administration, beginning at the arrow, of bradykinin, 5 ng/kg; c intracoronary administration of bradykinin, 10 ng/kg; d intracoronary administration of bradykinin, 30 ng/kg; e electrical stimulation of the left inferior cardiac nerve activating the afferent fiber; the biphasic first deflection is the artifact of the stimulus, and the second biphasic deflection is the action potential of the fiber. The approximate length of the nerve was 8 cm. The conduction velocity calculated for this fiber was 0.45 m/s. f Mechanical probing, marked by a bar, of an area of the external surface of the left ventricle: notice the after-discharge which is typical of nonmyelinated afferent fibers. (From Lombardi et al. 198 lb) 32 A. Malliani

from the coronary arteries: in the cat, a satisfactory isolation of the pericoronary nerve from the left main coronary artery is possible (Brown 1967; Casati et al. 1979). Both myelinated (Brown 1967; Malliani et al. 1973b; Uchida and Murao 1974b;Bosn]ak et al. 1979) and nonmyelinated (Uchida andMurao 1974b; Casati et al. 1979) ventricular sympathetic afferent fibers are excited during interruptions of coronary flow. Following coronary artery occlusion, excitation of myelinated fibers began after a mean of 80 s (Fig. 11), whereas only approximately 15 s elapsed before nonmyelinated fibers were activated (Fig. 12) (Malliani et al. 1973b; Casati et al. 1979; Lombardi et al. 1981b). The excitation of the myelinated ventricular afferent fibers occurred only when the heart was markedly dilated and thus had a long latency: moreover, when cardiac massage was performed, because of ventricular fibrillation, the consequent reduction in cardiac size was clearly accompanied by a decreased receptor discharge (Fig. 11 e). All these facts point to a predominant mechanosensitivity for the myelinated ventricular afferent fibers, a conclusion also reached by Uchida and Murao (1974b) and Bosn]ak et al. (1979). It is interesting to note that afferent cardiac vagal fibers were excited after interruption of left coronary artery perfusion after a mean latency of 42 s (Recordati et al. 1971). The shorter latency for excitation of nonmyelinated ventricular afferent fibers may indicate either a different level of mechanosensitivity or a greater responsiveness to chemical factors. On the other hand, Uchida and Murao (1974b) observed in the dog shorter latencies for the excitation of myelinated afferent fibers (about 21 s) than for nonmyelinated fibers (about 35 s). The discrepancy with the preceding data is likely to depend on the technique used, since the Japanese authors occluded the anterior descending branch of the left coronary artery: it is possible that the mechanical stimulus of occlusion directly affected nearby nerve fibers or receptive fields. A similar explanation may also apply to the short latencies for excitation of ventricular myelinated afferent fibers found by Bosn]ak et al. (1979). The different latencies for the activation of myelinated and nonmyelinated afferent fibers may be relevant to the onset of reflex effects and pain (Casati et al. 1979;Malliani and Lombardi 1982).

Effects of Chemical Substances. Sympathetic ventricular receptors with nonmyelinated fibers display a marked responsiveness to chemical substances such as bradykinin, potassium, acids, veratridine. These substances have been applied topically to the epicardial surface (Uchida and Murao 1974a, c, d, 1975; Nishi et al. 1977; Baker et al. 1980; Coleridge and Coleridge 1980), injected i.v. (Nishi et al. 1977), or administered by the Cardiovascular Sympathetic Afferent Fibers 33

Fig. 13. Responses of afferent im p//s 4.0- sympathetic nonmyelinated fiber with left ventricular endings to various experimental interventions. AO aortic occlu- 3.0 sion; LCO interruption of the perfusion of the left main coronary artery; BK 5 ng and 2.0 BK 10 ng, intracoronary administration of bradykinin, 5 ng/kg and 10 ng/kg; n number of fibers studied; *P < 1.(~ 0.001. (From Lombardi et al. 1981b)

AO LCO BK5ng BKlOng O= 23 23 23 16 control stimulus

intracoronary route (Brown and Malliani 1971; Malliani et al. 1973; Lornbardi et al. 1981 b) (Figs. 12b-d, 13). On the basis of the experimental findings two different general conclusions have been reached. Some authors found that all the left ventricular sympathetic receptors with nonmyelinated fibers (Lombardi et al. 198 lb) and a large proportion of cardiac sympathetic receptors with myelinated fibers (Nishi et al. 1977) displayed properties of low-threshold "polymodal" receptors. This term (Burgess and Perl 1973) indicates that the receptor zone is considered sensitive to mechanical and chemical stimuli, although a transducer mechanism that can account for such dual responsiveness has not yet been found (Leek 1977). In fact, due to their mechanosensitivity, all these receptors have a spontaneous impulse activity in the presence of adequate hemodynamic conditions. Low doses of chemical substances often appear capable of increasing such a mechanosensitivity, suggesting a phenomenon of "sensitization" (Nishi et al. 1977; Lornbardi et al. 1981b). On the other hand, Uchida and Murao (1974a, c, d, 1975) found silent ventricular sympathetic nonmyelinated afferent fibers that became active only after the administration of chemical substances: hence they concluded that a large proportion of these ventricular receptors are purely chemosensitive. This discrepancy deserves some comments. If the analysis is restricted to nonmyelinated ventricular sympathetic afferent fibers, the claim for purely chemosensitive endings is based on the appearance of action potentials from previously silent ventricular afferent fibers elicited by the epicardial application of chemical substances. However, the same authors (Ueda et al. 1969; Uchida et al. 1974) report a significant number of fibers that display mechanosensitivity to probing and yet are devoid of spontaneous activity. In all such cases, it is possible that the hemodynamic conditions in the heart were below threshold for some mechanosensitive 34 A. Malliani

endings, thus causing their fibers to remain without background discharge. In addition, it should be noted that topical application of chemical substances to the epicardial surface in the concentrations used might directly excite the fibers en passage (Khayutin et al. 1976), while a superficial probing of the beating heart (Uchida et al. 1974; Uchida and Murao 1974a, d, 1975) was probably not adequate to assess the existence of mechanosensitive fields if they were located deeply in the ventricular mass (Casati et al. 1979). Finally, Baker et al. (1980) claimed to have identified ten ventricular receptors that were "primarily" chemosensitive. In fact, the receptors said to have such specific transducing properties had a spontaneous impulse activity of 0.3 +- 0.3 imp/s that increased to 0.8 -+ 0.3 imp/s during a 50 mmHg rise in mean aortic pressure, i.e. they increased almost three times their firing during a physiological increase in aortic pressure. A similar change was reported for these ventricular mechanoreceptors (Casati et al. 1979). Other differentiating criteria were considered to be their unrespon- siveness to light superficial probing and their afterdischarge following strong mechanical stimulation: again these are typical properties of deeply located ventricular mechanoreceptors (Casati et al. 1979). In short, this population of so-called primarily chemosensitive receptors appears indis- tinguishable from other polymodal receptors.

Cardiac Nociception. It is generally accepted that the sympathetic nerves are essential to the perception of cardiac pain (Yonnesco 1921; Leriche and Fontaine 1927; Sutton and Lueth 1930; Lindgren and Olivecrona 1947; White 1957; Brown 1967). However, this notion does not solve the more analytical problem of whether noxious events, likely to be algesic, induce only an intensification in the tonic discharge of the sympathetic sensory endings or recruit instead silent fibers which possess a specific nociceptive function. This problem is part of a more general question concerning the peripheral mechanisms for nociception, for which two main hypotheses have been considered: they are the "intensity" or "specificity" theories (Perl 1971). The "intensity" hypothesis assumes that pain results from an excessive stimulation of receptive structures normally stimulated at lower levels. Alternatively, pain may be conceived as a "specific" sensation; that is, the product of the excitation of a well-defined nociceptive apparatus, the functional characteristics of which make it responsive only to a limited class of events, "noxious" stimuli that threaten the integrity of a tissue (Sherrington 1906). "In absence of previous insults.., sensory units fitting the criteria for nociceptors do not have background activity" (Burgess and Perl 1973). The "specificity" hypothesis would be consistent with the findings of Uchida and co-workers who have repeatedly reported the existence of a Cardiovascular Sympathetic Afferent Fibers 35 large population of afferent sympathetic fibers with ventricular endings, normally silent and excited during coronary occlusion or by chemical substances (Uchida and Murao 1974b, d, 1975). This hypothesis has also been recently privileged by Coleridge and co-workers (Baker et al. 1980; Coleridge and Coleridge 1980); however, their cardiac nociceptors all had a background activity. On the other hand, in our studies, we never observed a recruitment of silent afferent sympathetic cardiac fibers either following stimulation of the cardiac nerves or coronary occlusion (Malliani et al. 1973b; Casati et al. 1979). More recently, the intracoronary injection of bradykinin, a natural algesic substance (Guzman et al. 1962), suspected to take part in the genesis of cardiac pain (Bureh and De Pasquale 1963), was adopted as a tool for exciting silent chemosensitive ventricular receptors (Lombardi et al. 1981 b). However, intracoronary administration of bradykinin never recruited silent afferent fibers, a result which confirmed a previous study in which the drug was applied topically to the epicardium and the effects on active myelinated sympathetic afferent fibers were studied (Nishi et al. 1977). The conclusion seems inescapable that sympathetic cardiac receptors possess some degree of mechanosensitivity and have a spontaneous firing if the hemodynamic conditions are in the normal range. Accordingly, the "intensity" hypothesis seems to be the most appropriate to account for the functional properties of the neural substratum subserving cardiac nociception (Lombardi et al. 1981b; Malliani and Lombardi 1982).

5.3 Coronary Receptors

Brown and Malliani recorded impulse activity of afferent cardiac sympathetic nerve fibers that were excited by increases in coronary flow and pressure and by occlusion of the coronary sinus (Malliani and Brown 1970; Brown and Malliani 1971). Some of the fibers were also activated by interruption of left coronary artery flow leading to myocardial ischemia and by chemical substances (veratridine, acids). In these experiments, light mechanical stimuli were applied to the beating heart in order to localize the receptive fields that appeared to be in close proximity to the left main coronary artery. In my opinion these coronary receptors cannot be distinguished from other ventricular receptors that are also excited by increases in coronary flow and pressure (Malliani et al. 1973b, 1975a). With regard to the problem of cardiac nociception discussed earlier, Brown and Malliani (1971) observed a few silent fibers that became active during interruption of the coronary artery perfusion (Fig. 14). Such 36 A. Malliani

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I J lOs Fig. 14. Effect of myocardial ischemia on an afferent cardiac sympathetic nerve fiber. Computer analysis. Fall in coronary pressure shown as an upward deflexion of bottom tracing. The fiber had no background activity. After 15-18 s a discharge appeared and persisted for some 20 s after flow was recommenced. Each action potential gave a point on the frequency histogram; all spikes were superimposed for the inset. (From Brown and Malliani 1971 ) recruitment was interpreted as suggesting the existence of "specific" cardiac nociceptors excited by myocardial ischemia. It should however be pointed out that those recordings were obtained in spinal animals with a lower than normal arterial pressure, a fact that might have resulted in the lack of spontaneous firing of cardiac mechanoreceptors.

5.4 Receptors in the Large Thoracic Vessels

The endings of myelinated nerves on blood vessels were described at the end of the nineteenth century (Dogiel 1898). Usually they were regarded as subserving a sensory function (Woollard 1926). Some of the afferent nerve fibers from receptors in the large thoracic vessels were traced to the stellate ganglia (Muratori 1934). Electrophysiological experiments have recently provided convincing evidence on the existence of afferent sympathetic fibers, myelinated and nonmyelinated, innervating these vascular areas.

5.4.1 Aorta. Aortic mechanoreceptors with sympathetic nerve fibers were studied by Coleridge et al. ( 1975),Pagani (1975), Uchida (1975b), Malliani and Pagani (1976). Cardiovascular Sympathetic Afferent Fibers 37

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Fig. 15a--e. Activity of an afferent sympathetic myelinated nerve fiber with receptive field located in the proximal third of the descending thoracic aorta. Calculated conduction velocity 5 m/s. Tracings in a, b, c, d and e represent, from top to bottom, the endotracheal pressure (inflations upwards), the aortic and femoral arterial pressure, the ECG, and the nervous recordings, a Control; b occlusion of the descending thoracic aorta (indicated by the diverging blood pressure traces); e effects of an i.v. injection of 2 ~g angiotensin, performed just before the beginning of the record; d effect of a reflex blood pressure rise produced by occluding the right carotid artery (occlusion indicated by the bar); e effect of an abrupt increase in venous return produced by releasing, at the arrow, an occlusion of the inferior vena cava. (From Malliani and Pagani 1976)

In the experiments by Malliani and Pagani (1976) all myelinated afferent fibers were active at a mean systolic pressure of 139 mmHg, in phase with the aortic pressure pulses (Fig. 15a). Whenever aortic pressure was elevated by mechanical occlusion of the thoracic aorta (Fig. 15b), by injection of pressor drugs (Fig. 15c), by carotid sinus reflex (Fig. 15d), or by increasing the venous return (Fig. 15e), the impulse activity of all fibers studied increased markedly. Some myelinated fibers displayed repetitive discharges at high frequency with each pressure pulse (Fig. 15b). Maximal activity was attained while arterial pressure was rising and was 38 A. Malliani

related to the extent and rate of such a rise. Conversely hypotension always caused a decrease or suppression of the impulse activity that ceased when systolic blood pressure was lower than 102 mmHg. Myelinated aortic afferent fibers often had no spontaneous discharge in Uchida's experiments (1975b) and this is in conflict with our results. The nonmyelinated afferent fibers displayed functional properties similar to those observed for the myelinated fibers (Malliani and Pagani 1976). Thus, they had a spontaneous impulse activity at a mean systolic blood pressure of 132 mmHg (Fig. 16a). Although the spontaneous discharge appeared more erratic, if the slow conduction velocity was taken into account, most of the impulses corresponded to the aortic pressure pulses. All nonmyelinated fibers ceased to fire when systolic blood pressure was below 100 mmHg or when the animal was bled to death. Asphy- xia never increased their discharge, provided that it was not accompanied by an arterial pressure rise.

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Fig. 16a-i. Activity of an afferent sympathetic nonmyelinated nerve fiber with receptive field located in the distal third of the aortic arch. a Control; b occlusion of the descending aorta; e, d, e, f, h, and i, effects of stretching aortic wall by distending a latex balloon located in the distal part of the aortic arch after the animal had been killed by bleeding; g electrical stimulation of the left inferior cardiac nerve activating the fiber. Approximate length of the fiber, 5 cm. Calculated conduction velocity 1 m/s. Tracings in a and b as in Fig. 15. c, d, e, f, h, and i top tracing: pressure applied to the distending balloon; bottom tracing; nervous activity. (From Malliani and Pagani 1976) Cardiovascular Sympathetic Afferent Fibers 39

It is impossible to reconcile these data with those reported by Uchida (1975b): in his experiments nonmyelinated aortic afferent fibers had an activity mainly related to respiration and excited by asphyxia. This fact deserves some comment as it would have important pathophysiological implications. It may be that nonmyelinated aortic afferent fibers responsive to asphyxia exist in the dog (Uchida 1975b) but not in the cat (Malliani and Pagani 1976). However, from Uchida's data it is not possible to ascertain whether asphyxia was accompanied by an arterial pressure rise. Usually, in acute experimental conditions, some bleeding is necessary to maintain constant arterial pressure during asphyxia. It is also possible that the multifiber preparations from which the records were obtained included some postganglionic efferent activity, although details of the surgical preparations as described suggest that the preganglionic input to the stellate ganglion was interrupted. In five experiments, Malliani and Pagani (1976) studied, post mortem, the functional properties of myelinated and nonmyelinated aortic afferent fibers. Figure 16 shows an example of one of these experiments while recording from a nonmyelinated fiber. The fiber was strongly excited in vivo by increases in aortic pressure but with an irregular rhythm, due to cardiac arrhythmias accompanying the abrupt pressure load (Fig. 16b). When an aortic balloon was inflated (Fig. 16c-i), the highest impulse frequencies were attained during the rising phase of the pressor stimulus, followed thereafter by an adapted discharge (Fig. 16e, h). A dynamic component of the stimulus was also demonstrated by reaching the same level of absolute pressure at different speeds (Fig. 16c, d) or from different initial pressure (Fig. 16e, f). Finally, a response was observed which might be attributed to receptor fatigue and/or mechanical alteration of the vascular wall: in Fig. 16h a pressure rise produced a much higher activation of the impulse activity than that illustrated in Fig. 16i where the same pressure step was applied after the stimulus had been sustained for 100 s and just released for a few seconds. In the study by Malliani and Pagani (1976), 35 out of 24 aortic sympathetic fibers were found, post mortem, to have a single spotlike receptive field, while 11 had multiple receptive fields (from two to four): these were usually located in nearby aortic areas and, in addition, in other proximal portions of the arterial tree originating from the aorta (intercostal arteries, left subclavian artery, innominate artery, coronary artery), or in the adjacent pleura and connective tissue. Earlier anatomical observations (Wollard 1926) had in fact indicated that vascular sensory fibers could terminate in the adventitia of an artery by means of one branch and in the adjacent connective tissue by means of another branch. 40 A. Malliani

Coleridge and co-workers (1975) were the first to report afferent sympathetic fibers with multiple endings supplying distant cardiovascular areas. Out of 85 single afferent fibers, 48 fibers each had a single ending and 37 had 2-9 endings (average 4). Of the fibers with multiple endings, 26 innervated single organs (left ventricle, left atrium, pericardium, aorta, pulmonary artery, lung, trachea, esophagus and pleura). Eleven fibers innervated two or more structures, e.g., on fiber supplied endings in aorta, pleura, bronchus, and esophagus. In the opinion of Coleridge and co-workers these findings suggest that these sympathetic afferent fibers are unlikely to provide the central nervous system with specific information on events in a particular organ (Coleridge et al. 1975, 1978). This may perhaps hold true for those fibers, first described by Holmes and Torrance (1959), that most often have no spontaneous discharge and that seem only indirectly influenced by hemodynamic events as they innervate large portions of the pleura and the connective tissue surrounding the various thoracic organs. On the other hand, multiple but nearby cardiac sensory fields (Malliani et al. 1973 ; Nishi et al. 1977) are likely to signal similar local events. As for the aortic sympathetic mechanoreceptors, even with their possible satellite endings in the perivascular structures, they appear sensitive to hemodynamic stimuli and, for instance, quite well suited for signalling pulsatile aortic stretch. Indeed, were this to be their function, I do not think that a less specific message would reach the nervous centers if the receptor areas were not only located on the aorta but on the intercostal arteries as well, since aorta and nearby arterial rami do not usually have a different hemodynamic regimen. It should also be appreciated that mechanical probing, even if performed in the most appropriate conditions, indicates only a possibility for a normal receptor transduction but surely cannot determine, in the presence of multiple sensitive areas, whether action potentials originate only from one site or whether all of them participate randomly in this function. Thus the answer to the question of specificity must be defined from a study of the behavior of the receptors rather than from what we assume may be their potentials.

5.4.2 Pulmonary Artery. Nishi et al. (1974) provided a very careful study of the afferent sympathetic myelinated fibers innervating the wall of the pulmonary artery. The receptor fields were localized, post mortem, and most of them were in the distal part of the extrapulmonary tract of the pulmonary artery. These mechanoreceptors had spontaneous impulse activity that did not occur with each pressure pulse, but when they did appear the impulses were in phase with the upstroke of the arterial pressure pulse. When mean pulmonary arterial pressure was raised, impulses occurred during each cardiac cycle. Cardiovascular Sympathetic Afferent Fibers 41

Acetylcholine also excited the receptor discharge but this was interpreted as the result of a simultaneous rise in pulmonary arterial pressure. As expected, a reduction in pulmonary arterial pressure obtained by bleeding the animal caused a reduction in the impulse firing.

5.4.3 Pulmonary Veins. Nonidez (1941) observed that the pulmonary veins of previously sympathectomized cats contained no receptor endings. In his opinion this indicated that the sensory fibers innervating these vessels might run in the sympathetic nerves. Using electrophysiological techniques Lombardi and co-workers (1976) identified afferent sympathetic myelinated nerve fibers which had their endings on the pulmonary veins, thus confirming Nonidez's deduction.

200--., mmHgJ [-20 0 . ^ e, AA.,%~/~/L-A/~'J~ ~ _ _ |cm H20 20- I L 0 cmH2Oj 0 ~, I I ] J !I J l_i ! J I i.l r J. r I i I 1 J.] l I ] !r !l Ii rtl I I i I I

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Fig. 17a-c. Nervous activity of a single afferent sympathetic fiber innervating the left superior pulmonary vein. In each display recordings are, from top to bottom: ECG, systemic blood pressure, right atrial pressure, left atrial pressure, and nervous activity. a Constriction of the pulmonary artery; b i.v. injection of 5 ml warm saline; c progressive rising of arterial blood pressure induced by the i.v. injection of 5 #g noradrenaline. (From Lombardi et al. 1976) 42 A. Malliani

The receptive fields were relatively small (restricted to a few millimeters) when compared with other receptive fields observed by the same workers in other sites of the cardiovascular system. Moreover, each fiber had a single field and all were restricted to the pulmonary veins although they extended to the atrial junctions. However, there is some disagreement on this point as Coleridge and co-workers stated (1978) that in their experience the pulmonary veins seem to receive as large a proportion of fibers with multiple endings as do other cardiovascular regions. Future work will probably clarify this discrepancy. All fibers had spontaneous impulse activity that was mainly in phase with atrial systole (Lornbardi et al. 1976). The discharge was increased whenever pressure in the left atrium and, consequently, in the pulmonary veins was increased, e.g.i.v, injection of warm saline (Fig. 17b), pressor drugs (Fig. 17c), or mechanical constrictions of the thoracic aorta. All fibers were also excited during forced inflation of the lungs. Conversely, impulse activity decreased during reductions in pulmonary venous pressure, however produced (Fig. 17a). In general, these sympathetic receptors appear particularly suitable to sense pulmonary congestion.

6 Reflexes Mediated by Sympathetic Afferent Fibers

The study of the reflex effects elicited by the stimulation of cardiovascular sympathetic afferent fibers has probably contributed more to the ap- preciation of the importance of this afferent pathway than the detailed analysis of the functional characteristics of its receptors. In fact, it has become progressively clearer that these afferent fibers constitute by no means a kind of redundant and less sophisticated channel of information, but that instead they mediate reflexes which are quite different from those subserved by the supraspinal cardiovascular afferent fibers. Much work on this topic has been carried out in various laboratories during the last 15 years (Malliani et al. 1975a; Brown 1979) and a brief summary of the approaches that can be used will provide an appropriate frame to a concise description of the results. 1. More or less restricted hemodynamic stimuli, capable of modifying the activity of cardiovascular receptors, can be applied while the reflex effects are detected by monitoring the impulse activity of efferent nerve fibers. A shortcoming of this approach is that the exact function of the recorded efferent fibers, isolated as they may be from a well-defined outflow, remains unknown. However, this type of experiment is likely to provide information on the complexity of neural mechanisms participating even in the simplest reflexes elicited with natural stimuli. Cardiovascular Sympathetic Afferent Fibers 43

2. The afferent sympathetic fibers can be stimulated electrically or their endings chemically and the reflex effects can be measured either by recording the impulse activity of efferent visceral nerve fibers or by measuring cardiovascular target functions. Although the electrical stimulation can be performed with graded currents and various frequencies, these experiments are likely to suffer from the artificiality of activating simultaneously and at the same frequency fibers that in normal conditions would never fire synchronously. Thus the interneuronal modulations are likely to be severely distorted. On the other hand, a discrete chemical stimulation of the endings has the advantage of respecting the impulse generating capabilities of the "polymodal" receptor (Burgess and Perl 1973). How- ever, if larger doses are used, it becomes progressively more likely that the preterminal regions of the fibers may also be excited, and thus the stimulus bypasses the function of the generator potential. Not all chemical substances can be considered in the same category, for instance a natural substance like bradykinin should surely be preferred to a drug like veratridine. Finally, a chemical substance can be administered locally at doses incapable of producing direct general cardiovascular effects, thus any possible reflex would be easily detectable. 3. A hemodynamic disturbance can be simulated by an appropriate mechanical stimulus that does not alter, per se, the general hemodynamic conditions, and the reflex effects can be studied as hemodynamic or nervous responses.

6.1 Acute Experiments

Our experiments on reflexes mediated by cardiovascular sympathetic afferent fibers began with the observation that coronary occlusion could reflexly alter the firing frequency, most often toward excitation, of preganglionic sympathetic fibers (Malliani et al. 1969a, b). Recordings were obtained from single fibers isolated from the left third thoracic ramus communicans (T3), which is known to contribute to the innervation of the heart (Bronk et al. 1936;Pannier 1946; Randall et al. 1957). As the reflex response was present in animals with the vagi and spinal cord cut, a cardiocardiac spinal sympathetic reflex was proposed, the afferent and efferent pathways of which were both in the sympathetic nerves. However, the reflex was also present in animals with intact neuraxes and in unanesthetized decerebrate preparations: in cases where the baroreflex could be operative, the increased sympathetic discharge occurred in absence of any decrease in arterial pressure. In the section on human pathophysiology (p. 63-65), the potential importance of this reflex will be discussed. 44 A. Malliani

From a historical point of view, there was little in the literature to indicate that an excitory reflex could be elicited from the heart through an afferent sympathetic limb. In 1940, De Waele and Van De Velde (1940) claimed that cardiac receptors, activated by reduced venous return, could mediate a hypertensive reflex. Although their analysis of the mechanical or chemical stimuli capable of inducing the phenomenon was largely inadequate, they still made the remarkable observation that a mechanical manipulation of the heart could produce a hypertensive response which was probably reflex in nature as its afferent limb could be interrupted by sectioning the higher thoracic dorsal roots. Subsequently, Taquini and A viado (1961) found that a partial occlusion of the pulmonary artery could increase pulmonary blood flow. The increased flow was present after vagotomy and in spinal animals and appeared to depend on intact sympathetic innervation. To the best of my knowledge this was the scanty experimental evidence, before our own observations, on the possibility of eliciting excitatory reflexes from the heart, through afferent sympathetic fibers. Recent- ly, however, Felder and Thames (1979, 1981) questioned the existence of the reflex described by Malliani et al. ( 1969a, b), which, in their opinion, is present only in animals submitted to a spinal section. These findings are worth detailed analysis in view of their overall relevance to the reflexes mediated by sympathetic afferent fibers and because of more general methodological implications. In the first paper by Felder and Thames (1979) the specific search for an excitatory reflex mediated by cardiac sympathetic afferent fibers was carried out on dogs after acute sino-aortic denervation and vagotomy: this procedure was likely to have increased sympathetic activity near to a maximal level (the heart rate was 220 beats/min) a point accepted and discussed in the paper. Nevertheless in 1980 1 suggested that these high baseline levels of sympathetic efferent activity prevented the observation of an excitatory reflex: indeed, careful analysis of their published data makes it clear that they sometimes observed an excitatory response after sinoaortic denervation and vagotomy (Felder and Thames 1979, Fig. 3). In those animals in which an excitatory response was detectable, the heart rate was lower and it is possible therefore that their baseline conditions had a less abnormally enhanced level of sympathetic activity. However, the authors were concerned about the level of the baseline sympathetic activity and accordingly performed a new series of experiments (Felder and Thames 1981). The influence of the cardiac sympathetic afferent fibers on changes in sympathetic discharge to the heart during coronary occlusion was studied in dogs with an intact or interrupted neuraxis. In experiments on dogs with an intact neuraxis, basal activity in the cardiac sympathetic nerves was maintained at moderate or low levels by increas- Cardiovascular Sympathetic Afferent Fibers 45 ing the perfusion pressure in both carotid sinuses. It was concluded that an excitatory cardiocardiac sympathetic reflex can be demonstrated in dogs with the spinal cord sectioned but not with spinal cord intact. More explicitly it was suggested that cardiac sympathetic afferent fibers are not likely to mediate reflexes during myocardial ischemia in humans and therefore a classical and exclusive nociceptive function was the most appropriate role for sympathetic afferent fibers. However, the following comments should be considered: 1. An increased carotid sinus pressure could not only decrease the control sympathetic efferent discharge but severely depress the mediation of the reflexes either at a presynaptic or interneuronal level, similar to that known to be exerted on somatic reflexes when inhibitory supraspinal structures are activated (Carpenter et al. 1966; Engberg et al. 1968a, b). 2. Recordings from the whole ventrolateral cardiac nerve may not be a sensitive method of detecting excitation of sympathetic fibers as the cardiac sympathetic outflow is not excited as a whole (Malliani et al. 1969a, b). Moreover, the recent additional experimental findings are relevant. Weaver and her co-workers (1981) have recently published a study carried out on anesthetized cats using a carefully controlled protocol. Sympathetic and/or vagal cardiac afferent fibers remained intact while arterial baroreceptors were either left intact or denervated; a multifiber efferent sympathetic activity was recorded from the renal nerves. It was clearly shown that cardiac sympathetic afferent fibers can have excitatory influences on renal sympathetic efferent nerve activity and on arterial blood pressure during myocardial ischemia, and that this excitatory influences opposed the inhibitory respones mediated by cardiac vagal afferent fibers. Quite independently Lombardi et al. (1981a) studied cats on which a sino-aortic denervation had been performed 1 week before the experiment: the sympathetic efferent activity was recorded from fibers isolated from T3 (Fig. 18) with a nearly normal discharge under baseline conditions. In all cats occlusion of the left anterior descending coronary artery produced a significant increase in sympathetic cardiac efferent impulse activity; after vagotomy a similar coronary occlusion produced, in addition, a significant increase in left ventricular pressure, LVdP/dt, and mean arterial pressure (Fig. 18a). These responses were abolished by interruption of cardiac sympathetic afferent fibers (Fig. 18b). Such positive findings cannot be ignored. The finding of a cardiocardiac sympathetic reflex (Malliani et al. 1969a, b) raised the more general problem of whether the natural hemodynamic events could also elicit sympathetic reflexes in spinal animals. Numerous reports, starting with Sherrington's observations (1906), indicated the existence of vasomotor and sympathetic responses in experimental spinal animals (Langley 1924; Brooks 1933, 1935; Heymans et al. 46 A. Malliani

HR. ~2"OOb/mi n 160

[150 AP ~1 "mm

cot, o. LO

H R ~18Ob/min =140 ECG ~ .... F,----7 .... 7;ii;I-- IImLT7~: -

150 AP ~, - - 111 " -- ] Jill I I i? g , I, I ~,o

0.5 --~ - cor. '~O. ~ ~ 30 - S Lo/s b

Fig. 18a,b. Effects of occluding the left anterior descending coronary artery in a vagotomized cat. Sino-aortic denervation had been performed 1 week before. Between a and b the left steUate ganglion and the left thoracic sympathetic chain were removed down to T4, thus producing a partial "sympathetic deafferentation" that, however, was sufficient for the interruption of the afferent limb of the reflex. Tracings from top to bottom are the heart rate, the ECG, the arterial pressure, the impulse activity recorded from a multifiber preparation obtained from the left T3. (From Lombardi et al. 1981 a, unpublished work)

1936; Alexander 1945; Kuntz 1945; Downman and McSwiney 1946; Riehins and Brizzee 1949; Murkher]ee 1957; Beaeham and Perl 1964; Franz et al. 1966; Beacharn and Kunze 1969) and in paraplegic men (Guttmann and lChitteridge 1947). However, in spite of these descriptions it was not generally appreciated that spinal sympathetic centers may react reflexly in response to natural hemodynamic events, such as changes in blood pressure. The only suggestions for the existence of spinal vasomotor and sympathetic reflexes elicited by arterial pressure changes were to be found in accounts by Heymans et al. (1936) and, more recently, by Fernandez de Molina and Perl (1965); however, in both studies the reflex nature of these responses was not properly defined. In our experience (Malliani et al. 1971a) we found that when increases in systemic arterial pressure were produced in spinal vagotomized cats, the impulse activity of single preganglionic sympathetic fibers in T3 was either Cardiovascular Sympathetic Afferent Fibers 47 excited or decreased. The type of response was consistent for each individual fiber and was always reflex in nature. When, however, the increases in pressure were restricted to the coronary circulation, by changing the flow of a perfusing pump (Fig. 1) the preganglionic and postganglionic sympathetic discharge to the heart was always excited (Malliani and Brown 1970;Brown andMalliani 1971). We subsequently designed a series of experiments (Pagani et al. 1974) in order to analyze specifically the excitatory and inhibitory components of spinal reflexes: the activity of preganglionic sympathetic fibers isolated from T3 was tested during various hemodynamic and mechanical events in spinal vagotomized cats. Small rubber balloons mounted on catheters were inserted into the thoracic portions of the inferior vena cava and of the aorta, in the infundibular region of the left ventricle: these balloons could be inflated to obstruct blood flow. In addition, the pulmonary artery or

2OO1

b ._ L...= ...... J..[ .... J]l_l.[ .L[I ]_ ll .... t..i.l..IJ,, L "--] 1-- ! FI I l- I ]I-ITIlIII~II I1-1 rl-llr-I ll]

......

Fig. 19a-d. Increases or decreases in the discharge of the same sympathetic preganglionic neuron obtained with different stimuli. Tracings represent, from top to bottom, the carotid arterial blood pressure, the left atrial pressure, the right atrial pressure, the ECG and the nervous recording, a Stenosis of the pulmonary artery by a snare; b obstruction of the left ventricular outflow by inflating a balloon in the root of the aorta; c release of a transient occlusion of the inferior vena cava; d obstruction of the midthoracic aorta by a snare. Spinal vagotomized cat. (From Pagani et al. 1974) 48 A. Malliani

the aorta could be constricted by using snares. In these experiments it was found that when the stimuli were applied to the heart, thus eliciting possible cardiocardiac reflexes, an excitatory response was the rule (Figs. 19a-c, 22). Conversely, when the stimuli simultaneously affected cardiac and vascular receptors (rises in arterial pressure), the discharge of the same fibers was either increased or decreased (Fig. 19d). A cannula consisting of a stainless steel tube surrounded by an inflatable rubber cylinder was used to stretch the walls of the thoracic aorta without interfering with aortic blood flow (Fig. 20). In this manner it was possible to excite selectively aortic mechanoreceptors with a physical stimulus whose effect on

T1,

Fig. 20. Schema of a cannula, consisting of a stainless steel tube surrounded by an inflatable rubber cylinder, used to stretch the walls of the thoracic aorta without interfering with aortic blood flow aortic walls was the same as an increase in mean aortic pressure. The reflex responses of each preganglionic sympathetic neuron were either excitatory or inhibitory (Fig. 21), and they were consistent and in the same direction as observed during the increases in systemic arterial pressure. It was thus obvious that receptors located in various cardiovascular sites could exert different reflex effects on the same sympathetic preganglionic neuron. We therefore advanced the hypothesis that a prevalence of excitatory mechanisms existed in sympatho-sympathetic reflexes in which input and output were circumscribed to a few spinal segments, e.g., cardiocardiac reflexes, while inhibitory mechanisms were present in the reflexes involv-- ing more spinal segments, e.g., aorto-cardiac reflexes (Fig. 22). It is also possible that the specific activation of a population of afferent sympathetic Cardiovascular Sympathetic Afferent Fibers 49

200- m m H g. -----'~. ~ ~ ~ ~ ~i200 Oj [mmHg ~-0

b .I.I ..J. J .11 .[1., 1.1.1/1..11t11,I1.1.111II11.lillll I .11I... II,j. JL ~ ls

Fig. 21a, b. Effects of stretching the aortic walls (with the aortic cannula) on the discharge of two different (a and b) sympathetic preganglionic neurons. Tracings represent, from top to bottom, the endotracheal pressure (inflations upwards), the carotid and femoral arterial blood pressure, and the nervous recordings. Spinal vagotomized cat. (From Pagani et al. 1974)

INPUT OUTPUT Mechanical Electrical Chemical Vagal firing Stimuli

firing T -I

Stretch Fig. 22. Reflex responses of sympathetic and vagal efferent neurons elicited by the stimulation of afferent sympathetic fibers. Scheme derived from electrophysiological experiments. (From Malliani et al. 1975a)

fibers, i.e., the myelinated or the nonmyelinated ones, may also modulate the excitatory and inhibitory reflex components. Electrical or chemical stimulation of afferent cardiac sympathetic fibers was found to elicit a simultaneous inhibition of vagal efferent fibers and an excitation of sympathetic efferent fibers, both directed to the heart and isolated from the same cardiac nerve at its junction with the right atrium (Schwartz et al. 1973). This sympathovagal reflex (Fig. 22) represented a total overturning of the classic vagosympathetic circuitry. More- 50 A. Malliani over, these electrophysiological experiments suggested a synergistic excitatory effect on cardiac function mediated through an excitatory sympathetic reflex and a reduction in vagal restraint. Peterson and Brown (1971) were the first to assess the functional significance of reflexes mediated by sympathetic afferent fibers: they found a reflex increase in arterial pressure elicited by electrical stimulation of afferent cardiac sympathetic fibers. Subsequently it was found that similar electrical stimulations reflexly induced an increase in myocardial contractility (Malliani et al. 1972a), heart rate (Malliani et al. 1973a), and aortic smooth muscle tone (Pagani et al. 1975). In particular, when the increases in myocardial contractility could be induced with intracoronary injections of veratridine (Malliani et al. 1972a), conclusive evidence was obtained on the existence of cardiocardiac sympathosympathetic reflexes. Staszewska-Barczak et al. (1976), on the other hand, were able to demonstrate clearly the existence of excitatory cardiovascular reflexes elicited by the epicardial application of bradykinin and mediated by cardiac sympathetic afferent fibers. However, it still had to be proved that cardiovascular reflex responses could be elicited by natural stimulation of sympathetic mechanoreceptors. The observation that numerous sympathetic sensory endings could be identified in the walls of the thoracic aorta by their function and that a stretch localized to a segment of it could reflexly modify the activity of sympathetic preganglionic neurons (Pagani et al. 1974) seemed to offer a possible solution to this problem. A similar aortic cannula (Fig. 20) was used: in spinal vagotomized cats or in cats with an intact central nervous system but with sino-aortic denervation, stretch of the thoracic aorta, which did not interfere with aortic blood flow, induced significant increases in arterial blood pressure, heart rate, and maximum rate of increase in left ventricular pressure (Fig. 23a) (Lioy et al. 1974). These responses were eliminated by infiltrating the wall of the thoracic aorta with xylo- caine. In the adrenalectomized cats with intact central nervous system, reflex responses were reduced but were still statistically significant. Phen- oxybenzamine abolished the pressor response but not the increases in heart rate and dP/dt max. Propranolol drastically reduced the increases in heart rate and dP/dt max but not the pressor response (Fig. 23b). Thus, aortic stretch induced an increase in sympathetic nerve efferent activity affecting the heart, the peripheral vessels, and probably the adrenal glands through a reflex present in animals with intact central nervous system and with a spinal section. Several other reports have defined responses which are mediated by sympathetic afferent fibers. Weaver (1977) found that low-frequency electrical stimulation of cardiopulmonary sympathetic afferent fibers could reflexly decrease the arterial blood pressure and efferent impulse Cardiovascular Sympathetic Afferent Fibers 51

a b 200

50 - [ ° FAP~ _~,~ -- __ ./~ L50 Lv. 2l

,30s , Fig. 23a, b. Effects of stretching the thoracic aorta in a vagotomized cat with an intact central nervous system and both common carotid arteries occluded. CAP carotid artery pressure (recorded proximal to the point of occlusion). FAP femoral artery pressure. LVP ventricular pressure (all in mmHg). L V dP/dt rate of change of left ventricular pressure (mmHg/s). HR heart rate (beats/min). On the left of each section are fast-speed records of each variable. The aortic stretch is indicated by a bar. a Con- trol; b after administration of propranolol (1 mg/kg, i.v.). (From Lioy et al. 1974) activity in renal nerves; both effects were reversed to an excitation by increasing the frequency of the stimulating pulses. Purtock et al. (1977) similarly found that low-frequency stimulation of thoracic sympathetic afferent fibers induced renal vasodilation, while high-frequency stimulation induced renal vasoconstriction. Hence these reports confirm that it is also possible to elicit reflex inhibitory effects which are mediated by sympathetic afferent fibers. The experiments summarized above demonstrate that afferent sympathetic nerve fibers can mediate cardiovascular reflexes. However, as to their physiological significance, we realized that most responses were obtained in anesthetized animals in which the buffering influences exerted by vagal and carotid sinus afferent fibers no longer existed. It was totally unproven whether such reflexes could exist in the fully innervated animal and whether a substantial activation of the cardiovascular sympathetic afferent fibers could occur in the conscious state in the absence of pain.

6.2 Chronic Experiments

In order to achieve some perspective on the natural role of excitatory reflexes there was a need for models that could reveal, in the unanesthetized 52 A. Malliani state and possibly in the presence of an intact innervation, functioning cardiovascular reflexes mediated by sympathetic afferent fibers. The first model (Malliani et al. 1975a; Bishop et al. 1976) consisted of cats with a chronic spinal section performed at the level of the eighth cervical segment (Fig. 24), breathing spontaneously, and with normal arterial pressure. In these animals the cardiac innervation consisted of two independent loops, one vagovagal and one sympathosympathetic. Atro- pine (0.5-0.7 mg/kg) was administered i.v. to block the outflow of the vagal loop. Due to the chronic spinal section, the sympathetic efferent tonic activity was presumably low as suggested by the mean baseline heart rate (109 beats/min) and, after atropine, 127 beats min. Under these conditions, i.v. infusion of saline (50-150 ml) over a period of 2-5 min resulted in a significant tachycardia (Fig. 25a): the maximal increase observed was 22 beats/min, while the average was 10 beats/min. A section of thoracic dorsal roots T 1-6 and of the spinal cord between T6 and T7 abolished the response (Fig. 25b), thus proving that it was reflexly mediated through sympathetic afferent fibers.

Cs T1

I Low pressure1 j L4 Fig. 24. Schema of the animal model used in the experiments by Malliani et al. (1975a) and Bishop et al. (1976). A chronic spinal section was performed at the level of the eighth cervical segment; atropine was administered to block the vagal outflow. The cardiac innervation with a possible reflex function was thus restricted to a sympathosympathetic loop Cardiovascular Sympathetic Afferent Fibers 53

A tachycardia evoked by i.v. infusions and thought to be reflexly mediated by sympathetic afferent fibers was also described in anesthetized dogs (Gupta 1975; Gupta and Singh 1977). Thus the increase in heart rate following infusions first described by Bainbridge (1915) appears to be mediated at least in part by afferent sympathetic fibers. Such a reflex mechanism may play an important role in the course of congestive heart failure. Intravenous infusion could activate many different cardiovascular sympathetic mechanoreceptors although those innervating the atria (Fig. 3) and the pulmonary veins (Fig. 17), i.e., low pressure areas, were likely to be involved. On the other hand, it is also clear that in intact animals an i.v. infusion may reflexly modify the cardiac frequency, through sympathosympathetic, sympathovagal, vagosympathetic (Linden 1979), and

a F190 ~,~_...~,-~ fb/r"i~

HR-. L140

RAP"....~ _ '...... r...... ~ .... t-o

1-150

,3o ...... 9.5s

HR ~...... _. _ , ..... _ - L140

~150 AP ~ III I

30 0.5s , Fig. 25a, b. Analogue recording of heart rate (HR), right atrial pressure (RAP), arterial pressure (AP), and electrocardiogram (ECG) in chronic spinal cat in control conditions and during i.v. infusions, a Sham preparation (dorsal roots T1-T6 isolated but not cut); b after section of dorsal roots T1-T6 and of spinal cord between T 6 and TT. Record- ings in b were obtained 36 h after those shown in a. Infusions indicated by bars. (From Bishop et al. 1976) 54 A. Malliani

vagovagal circuits. This complexity is easily illustrated by the effects of anesthesia on the reflex heart rate response: from a consistent tachycardia response in unanesthetized animals (Horwitz and Bishop 1972) one may observe either tachycardia or bradycardia depending on the initial heart rate (Coleridge and Linden 1955; Jones 1962) during anesthesia. Apart from these considerations, the experiments described above (Bishop et al. 1976) were the first to demonstrate that a natural hemodynamic stimulus could elicit a reflex cardiovascular response through a sympathosympathetic circuit in the unanesthetized animal. However, the presence of a chronic spinal section was an important disadvantage when evaluating the significance of this reflex and its interplay with other regulatory mechanisms. A second model has also been used and consisted of stretching a short segment of the thoracic aorta, without obstructing the aortic flow, in a conscious dog with an intact cardiovascular innervation. In the initial experiments (Malliani et al. 1979) a metal cannula covered by a rubber cylinder, similar to that used in acute experiments (Fig. 20) was implanted. Subsequently (Pagani et al. 1980, 1982) a Teflon stiff core was employed for the cannula which allowed the use of an ultrasound technique using piezoelectric crystals to measure external aortic diameter during control conditions and during the stretch. Catheters for pressure recordings, piezoelectric crystals, and the aortic cannula were all implanted under general anesthesia and aseptic conditions.

HEART RATE (b/min)

ARTERI.a PRESSU (mmHg)

MEAN PRESSU (rnmHg)

BALLO0 PRE~SSU

lmin.~

Fig. 26. Effects of a progressively increasing aortic stretch on arterial pressure and heart rate in a conscious dog. The distending balloon pressure, which obviously does not correspond to the pressure effectively applied to the aortic walls, is displayed in the bottom tracing as an index of the progressive stretch. (From Malliani et al. 1979) Cardiovascular Sympathetic Afferent Fibers 55

After recovery from surgery, aortic diameter was increased 9.6% + 0.4% from 16 + 1 mm by inflating the implanted cannula. This stretch, which did not evoke behavioral changes or any overt pain reaction, produced a rise in mean aortic pressure of 31% + 3% from 100 + 3 mmHg and an increase in heart rate of 20% + 3% from 91 + 3 beats/min (P < 0.01) (Pagani et al. 1982). An example of these pressor reflexes is shown in Fig. 26; once a threshold level was exceeded, progressive increases in arterial blood pressure were obtained by augmenting distension. Alpha-adrenergic receptor blockade (phentolamine, 0.5-1 mg/kg body weight i.v.) abolished the arterial pressure response (Fig. 27). The reflex tachycardia was prevented by combined muscarinic and /~-adrenergic receptor blockade (atropine 0.2-0.3 mg/kg and propranolol 1 mg/kg, i.v.). The reflex nature of the response was, therefore, proven. The possibility that this sympathetic reflex might interact with baroreceptor mechanisms was also investigated, because such an interplay was

no-block 5min Alpha-block ,~,,.I..,h., hJ,.h., J,. ,h..h.*. h,. h. J..*l.,, h,,.h, d,..I.,, h..h.. . .I.h,hlJ,h,.,I.. d..I ...... hl.h.d..I.,,h.*l,,,,I,,,,h,,d..h,,,h,*,h,.h,i,h, PROXIMAL 20Of~ PRESSURE (mrnHg) 200 MEAN P. PRESSURE (mmHg) 0 20( DISTAL PRESSURE (mmHg) 20( MEAN D. PRESSURE (mmHg) 180 HEART RATE (beats/min) 6O AORTIC 19f DIAMETER (mm) 15" Fig. 27. Pressor and heart rate responses to stretch of the descending thoracic aorta in a conscious dog. The initiation of aortic stretch (left panel) is indicated by the increase in aortic diameter. Notice the similar increase in both proximal and distal pressures, indicating the lack of direct mechanical obstruction to blood flow by aortic distension. After 5 min (middle panel), the pressor and heart rate responses were still maintained. Alfa-adrenergic blockade (phentolamine 1 mg/kg) (right panel) virtually abolishes the pressor response to aortic stretch, while an increase in heart rate is still present. (From Pagani et al. 1982). 56 A. Malliani

suggested by a previous electrophysiological study (Schwartz et al. 1973). The slope of the regression of the electrdcardiographic R-R interval on the systolic pressure increase induced by phenylephrine (50/ag/kg i.v.) was used as an index of baroreceptor sensitivity (Smyth et al. 1969). Aortic stretch produced a significant reduction in baroreflex sensitivity (57% -+ 7% from 18 -+ 2 ms/mmHg,P< 0,01). Additionally, the arterial pressure response increased after carotid nerve section and vagotomy to 49% -+ 8% (Pagani et al. 1982). This observation not only confirmed that the afferent limb of the reflex was in the sympathetic nerves but also indicated that the baroreceptive and vagal afferent fibers were likely to play a restraining role. In Sect. 7, the possible significance of this pressor reflex will be analyzed further. In the third model (Pagani et al. 1981), we resorted to the intracoronary administration of bradykinin in the conscious dog. As described above, bradykinin produces marked activation of cardiac sympathetic afferent fibers (Uchida and Murao 1974d; Nishi et al. 1977;Coleridge et al. 1978; Baker et al. 1980; Lombardi et al. 1981b) and in addition it substantially excites afferent cardiac vagal nonmyelinated fibers (Kaufman et al. 1980). Catheters were inserted in the aorta and either the left circumflex or anterior descending coronary artery. A Doppler flow probe was also inserted around the same coronary artery for blood flow determinations and a solid state pressure gauge into the left ventricle (Pagani et al. 1981). Pre- liminary data indicated that bradykinin (100 ng/kg) injected into the cannulated coronary artery 1-2 weeks after surgery induced in the conscious animals a significant (P < 0.01) increase in mean arterial pressure (31% -+. 3% from 85 -+ 2 mmHg), in heart rate (34% -+ 3% from 84 -+ 9 beats/rain), as well as in left ventricular pressure, left ventricular dP/dt max (33%), and coronary blood flow. These changes were obtained in the absence of overt pain reactions and were also present after pretreatment with morphine (1 mg/kg, i.v.). The reflex nature of the blood pressure change was shown by its disappearance after ~-adrenergic receptor blockade with phentolamine (1 mg/kg, i.v.). Thus a pressor sympathetic reflex can be obtained in the conscious state from a fully innervated heart. In other studies on anesthetized animals, the intracoronary administration of bradykinin produced depressor reflexes (Neto et al. 1974) or either pressor or depressor reflexes (Reimann and Weaver 1980; Lombardi et al. 1982): the depressor component is mediated by vagal afferent fibers. These facts clearly indicate the fundamental role played by anesthesia, when several neural circuits are simultaneously activated, in determining the final response. In general it also appears that the concept, derived from experiments using veratridine in anesthetized animals (Von Bezold and Hirt 1867), that a chemical stimulus applied to the neurally intact heart always elicits a Cardiovascular Sympathetic Afferent Fibers 57 vagally mediated depressor response and that vagotomy is necessary (Coleridge and Coleridge 1979) to reveal pressor sympathetic reflexes is no longer tenable (Pagani et al. 1981). In the conscious state, it can be concluded that excitatory reflexes evoked by bradykinin and mediated by sympathetic afferent fibers usually predominate. In investigations into the algogenic action of bradykinin, larger doses (300-600 ng/kg) were injected into the cannulated coronary artery without eliciting pain reactions (Pagani et al. 1981). It is possible that some recent surgical injury, absent in our experimental conditions, may greatly facilitate the algogenic action of bradykinin (Guzman et al. 1962). How- ever, the absence of pain reactions in our chronic experiments was surpris- ing. I would suggest that visceral pain is more likely to result from the extreme activation of a spatially very restricted population of afferent sympathetic fibers (as it may occur during the localized mechanical abnormal- ities accompanying acute myocardial ischemia). Conversely, when activation of the sympathetic afferent fibers is widely distributed, some central inhibitory modulation (Wall 1976) may prevent pain mechanisms. Indeed, a systemic increase in arterial blood pressure produces a very substantial and widespread increase in the activity of cardiovascular sympathetic afferent fibers. Yet, in humans a marked increase in systemic arterial pressure is not painful, although it is often accompanied by some discomfort. In short, the intracoronary injection of bradykinin would produce a widespread activation of the cardiac sympathetic afferent fibers and thus not elicit pain. This hypothesis can be tested experimentally, although pain is a conscious experience which can be explored only indirectly with our laboratory animals. Thus we have obtained substantial evidence that excitatory cardiovascular reflexes can take place in animals with an intact innervation and that a significant activation of cardiovascular sympathetic afferent fibers can occur, in the conscious state, in the absence of pain. Finally it should be noted that the experiments on coronary occlusion in unanesthetized animals have not yet provided a clear answer on the possible role played by reflexes mediated by sympathetic afferent fibers. This uncertainty probably reflects the complexity of the experimental situation created by coronary occlusion: apart from the striking alterations in ventricular function (Pagani et al. 1978), myocardial ischemia can excite both sympathetic and vagal (Recordati et al. 1971; Thoren 1979) receptors. Thus, pressor and depressor reflexes could be activated from the heart simultaneously and, to a variable extent, both could interact with baroreflexes. In practice it was found that brief occlusion of the left circumflex coronary artery produced a rise in heart rate, a modest but significant fall in arterial pressure, and a slight increase in peripheral resistance (Peterson et al. 1973;Peterson and Bishop 1974). It was shown 58 A. Matliani that the tachycardia was due both to an arterial baroreflex and to a reflex from the heart: however, the afferent pathway from the heart was not investigated directly. In another study (Bishop and Petersen 1978), it was demonstrated that cardiac vagal afferent fibers mediate depressor reflexes from the heart during coronary occlusion. On the other hand, in the unanesthetized monkey, the occlusion of the distal part of the left anterior descending coronary artery elicited an increase in arterial pressure, heart rate, and LVdP/dt (Randall et al. 1978). It is clear that much more work is needed to unravel the complex interactions of the various reflex mechanisms accompanying acute myocardial ischemia in the conscious fully innervated animal.

7 The Positive Feedback Hypothesis

The common observation that arterial blood pressure in a resting man or in anesthetized animals is relatively constant and that powerful reflexes tend to counteract changes in pressure, provided the most factual basis to the teleologic concept of circulatory homeostasis. Accordingly, the sinoaortic negative feedback control system has been regarded for decades as the indisputable leader of this homeostasis. It was not until 1959 that an authoritative academic voice, that of Bard (1960), asserted in the opening lecture of an international symposium that suprabulbar influences must inhibit baroreceptor function when an organism has to maintain an elevated heart rate in the face of an increased arterial pressure, as happens during periods of stress or exercise. Moruzzi (1940) had already shown that carotid sinus reflexes could be inhibited by stimulation of anterior vermis of the cerebellum. It was, however, only the subsequent progressive exploration into the hemodynamic conditions occurring during exercise or emotion (Rushmer et al. 1960; Bergamaschi and Longoni 1973; Vatner and Pagani 1976) that revealed that the negative feedback baroreflexes could change to such an extent (Bristow et al. 1971 ; Coote et al. 1971; Smith 1974; Vatner and Pagani 1976) that they become sometimes quite permissive by standers in those circulatory "storms" (Lewis 1931). As for the mechanisms through which baroreflexes could be attenuated, early attention was paid to the suprabulbar structures (Hilton 1966; Smith 1974). Subsequently it was realized that the mechanisms inhibiting the baroreflexes could be activated also from the periphery, through vagal (Vatner et al. 1975) or somatic (Kumada et al. 1975) afferent nerve fibers. These mechanisms could provide an explanation for the variable efficacy Cardiovascular Sympathetic Afferent Fibers 59 of baroreflexes; however the strategy of regulation through neural circuits would still be based exclusively on negative feedback operational systems. Our experimental data suggest an additional possibility. In an open loop model (Fig. 28, upper part) a stimulus likely to mimic the effects of an increase in mean aortic pressure on aortic mechanoreceptors, i.e., an aortic stretch, elicited an increase in systemic arterial pressure (and heart rate) through a sympathosympathetic reflex. This is indicated by the positive sign for this feedback mechanism, as opposed to the negative feedback characteristics of the baroreflexes (Fig. 28, lower part).

...... t SYMPATHETIC i feed-back AFFERENTS i signal I I I disturbanc( I Reference I error [ ~,.~~ ~@ Arterial signal '~- signal -- [ pressure :/ - I CNS

feed-back signal BARORECEPTORS I ~__

Fig. 28. Schema of suggested mechanisms underlying nervous control of arterial blood pressure regulation. Baroreceptors are indicated as the example of receptors that activate negative feedback mechanisms. The coexistence of inhibitory components in reflexes mediated by sympathetic afferent fibers is represented by the broken line. cars central nervous system; CV cardiovascular. (From Malliani et al. 1979)

We hypothesize that these positive feedback reflexes are tonically operative for two reasons: firstly, aortic sympathetic mechanoreceptors have a spontaneous impulse activity at normal arterial pressures (Malliani and Pagani 1976); secondly, the amount of aortic stretch necessary to initiate a pressor reflex produces an increase in aortic diameter that is comparable to that which accompanies rises in arterial pressure within the physiological range (Pagani et al. 1980, 1982). One consequence of this is the problem of the normal function of these excitatory reflexes. By the Darwinian hypothesis, of no less value in physiology than in morphology, every reflex must be purposive. But the assignment of a particular purpose 60 A. Malliani

to a particular reflex is often difficult and hazardous (Woodworth and Sherrington 1904). The positive feedback reflexes (Malliani et al. 1975b, 1979) should be considered as one component of those complex regulatory mechanisms which result from the interplay of multiple and independent peripheral loops and of multifarious possibilities of central integration. In the resting or anesthetized state, the supraspinal structures are likely to exert a restraining influence on these reflexes (Lioy and Szeto 1975; Pagani et al. 1982). It should also be kept in mind that reflexes mediated by sympathetic afferent fibers possess inhibitory components as well (Pagani et al. 1974) (Fig. 28). In brief, the negative feedback mechanisms frequently seem to act as the effective controllers of the overall cardiovascular regulation. However, even in these cases, positive feedback mechanisms could play a regulatory role in modulating the range of operation and stability of supraspinal cardiovascular reflexes. In this regard, it should be recalled that the sensitivity Of negative feedback baroreceptive control of heart rate could be markedly reduced during aortic stretch (Malliani et al. 1979; Pagani et al. 1982). Similarly, baroreflex control of heart rate was decreased during coronary occlusion (Takeshita et al. 1980). Thus, excitation of cardiovascular sympathetic afferent fibers is likely to modulate the activity of the structures that integrate baroreflexes through ascending pathways. In conclusion, in resting conditions positive feedback reflexes may behave discreetly while participating in the fine tuning of homeostasis. On the other hand, there are physiological conditions, such as exercise or emotion, in which the efferent sympathetic activity seems to be unrestricted. If a reflex must be purposive, an animal running away from a predator would find positive feedback mechanisms quite well suited for its goal. Conversely, pathophysiological states often suggest an involvement of mechanisms that are purposeless or even detrimental when their physiological function is removed: thus teleologic reasoning is not produc- tive. Arterial hypertension as a disturbance of regulation could, especially in its early phases, partly be the result of an increased sympathetic efferent activity. This increase, according to our hypothesis, may depend not only on an augmented central command but also on the peripheral action of sympathosympathetic loops exhibiting positive feedback characteristics. In fact, the mechanisms producing a sustained increase in sympathetic efferent activity may be similar to those in the decerebrate animal that are responsible for spasticity: Sherrington (1906) found that spasticity is removed by deafferentation. It was thus shown that an augmented central command was incapable in itself of causing a sustained increase in the postural tone but that a peripheral loop was necessary for its maintenance. In brief, we suggest that negative and positive feedback mechanisms may interact continuously to achieve the most adequate regulation for the Cardiovascular Sympathetic Afferent Fibers 61 various cardiovascular performances: if this is the case each specific hemodynamic condition, even those corresponding to the most stable resting states, would reflect some degree of interaction of opposite tendencies, a biological example of a true dialectic process. In paraplegic patients, cardiovascular sympathetic reflexes seem often to possess a savage power (Corbett et al. 1971a-c), which perhaps indicates the full potential of the system. "The phenomena of disease are thought to be purely adventitious; they are spoken of as 'pathological', and are supposed to bear no relation, even remotely, to any mode of response which has previously existed in the individual or the race". "Normally... (the more primitive responses) are suppressed because they would disturb the more discriminative response of higher centres; but they still remain capable of revival under conditions demanding urgent and impulsive action" (Head 1921).

8 GeneralProperties of Cardiovascular Sympathetic Afferent Fibers: A Summary

Afferent sympathetic nerve fibers with cardiovascular receptive endings display a tonic impulse activity in relation to normal and specific hemodynamic events. Their sensitivity to natural stimuli can be extreme: as in the case of atrial receptors that seem capable of detecting minimal alterations in atrial dynamics, even before these may be reflected by changes in atrial pressure (Malliani et al. 1972b). The spontaneous low firing rates of sympathetic afferent fibers was attributed, as a working hypothesis (Malli- ani et al. 1973b), to a special type of transducer, different from that of the vagal endings, possibly an end-net formation. Coleridge et al. (1978) emphasized, quite appropriately, "the curious discrepancy between the relative low rate of firing that is evoked when the ending is stimulated physiologically by an increase in transmural pressure and the high frequency response to even the lightest touch". There is no explanation for this common finding: one may simply suggest that even the lightest touch produces a generator potential that differs from those occurring normally and that is capable of a more efficient coupling with the electrically excitable conductile membrane (Grundfest 1966). Moreover, it cannot be excluded that probing may also directly excite the terminal parts of the conductile membrane. However, the basic low impulse activity of sympathetic afferent fibers should perhaps be considered in relation to the positive feedback mechanisms that they are capable of activating and, although un- explained, this low activity may then appear desirable. 62 A. Malliani

Coleridge et al. (1978) also wrote that "when one compares the brief and relatively modest response to even marked increases in pressure or volume with the dramatic effects of bradykinin and prostaglandin, one cannot help but feel that it is in their response to endogenous chemicals that afferent sympathetic endings find their true expression". I cannot agree with this statement for two reasons: high doses of bradykinin could directly excite the preterminal fibers (Khayutin et al. 1976) and in our experience, ventricular fibrillation could sometimes abruptly excite nonmyelinated ventricular afferent fibers even more than bradykinin (Figs. 9, 12). Yet, I do not think that the true expression of this afferent pathway is signalling ventricular fibrillation. The well-recognized nociceptive function of these afferent nerve fibers is likely to depend on their intense activation rather than the recruitment of a specific population of nociceptive units. This afferent neural channel, connecting the cardiovascular system to the spinal cord (Fig. 29), seems to subserve a tonic reflex function contributing to the complexity of the neural regulation of hemodynamic events. The excitation of this spinal input produces cardiovascular reflexes that are mainly excitatory in nature, although inhibitory components are also present. The reflexes mediated by sympathetic afferent fibers, when they only involve the sympathetic outflow, can be present in spinal preparations and therefore spinal structures appear sufficient to integrate them. However,

Fig. 29. Schema of the cardiovascular sympathetic innervation conceived as an input-output system interact- ing with supraspinal nervous mechanisms. (From Malliani 1981) Cardiovascular Sympathetic Afferent Fibers 63 this does not mean that supraspinal structures cannot be involved when the neuraxis is intact. In fact, it was proven that in anesthetized and unanesthetized animals the excitation of sympathetic afferent fibers could also modulate the sensitivity of supraspinal reflexes. As to the effect of spinal section on the magnitude of these reflexes, we never observed an increase but, if anything, a small decrease in their entity. Therefore, I would agree with Peterson and Brown (1971) and with Staszewska-Barczak and Dusting (1977), who stated that, after spinal section, the reflex responses to the stimulation of cardiac sympathetic afferent fibers are reduced, rather than with Felder and Thames (1981), who stated that a reflex mediated by cardiac sympathetic afferent fibers can only be present after spinal section. The acute effect of a spinal transection is quite different from the "'release of function in the nervous system" (Head 1921), a phenomenon that should require time. "If the fall of general blood-pressure be regarded as part, and a severe part, of the 'spinal' shock which ensures on spinal transection in the cervical region" (Sherring- ton 1906), one would suggest that this is the most frequent consequence of such an intervention, especially when not properly performed in terms of anesthesia and surgery. In the conscious state, potent pressor reflexes can be elicited in the absence of pain.

9 Human Pathophysiology

This section concentrates on the neural mechanisms likely to participate in the pathophysiological complexity of acute myocardial ischemia. Vari- ous laboratories have been accumulating, over the years, a great deal of pertinent data which largely anticipated clinical understanding. The experiments by Von Bezold and Hirt (1867) introduced the notion of vagally mediated depressor reflexes from the heart, which supported the intuition of Cyon and Ludwig (1866). Much time, however, had to elapse before depressor reflexes were found to be associated with experimental coronary occlusion (Costantin 1963 ; Dokukin 1964; Thordn 1979). An erroneous extension of finalistic interpretations from physiology to pathophysiology probably enabled the establishment of the opinion that all reflexes arising from the diseased heart had to subserve a function of decreasing its load. When we described the sympathetic excitatory reflex elicited by coronary ocelusion (Malliani et al. 1969a, b) we hypothesized that the reflex might have two opposite consequences in the course of human disease. On the one hand, increased cardiac sympathetic activity could signify increased myocardial oxygen consumption and facilitated arrythmias; on the other 64 A. Malliani

hand, a reflex increase in contractility might be an important mechanism to oppose ventricular dilatation and cardiogenic shock (Aviado and Schmidt 1955; Salisbury et al. 1960). Obviously, the hypothesis was not based on teleologic reasoning for the benefit of the patient but on the factual results of an increased sympathetic activity. Subsequently it was proved that the presence of a cardiac sympathosympathetic loop plays an important role in the arrhythmias associated with coronary occlusion (Schwartz et al. 1976) and that cardiac sympathetic afferent fibers can mediate a reflex increase in myocardial contractility (Malliani et al. 1972a). However, the link with human disease was almost nonexistent. The clinical work by Pantridge's group offered a new perspective and represented a milestone (Webb et al. 1972; Pantridge 1978). By showing that a majority of patients had signs of "autonomic disturbance" at the onset of an acute myocardial infarction and that excessive sympathetic activity (as revealed by tachycardia and/or hypertension) was more frequent in cases of anterior infarctions, whereas a vagal overactivity (as revealed by bradycardia and/or hypotension) was more frequent in inferior infarctions, they suggested the existence of specific mechanisms independent of pain and emotion or of a pure pump failure. Hence, pressor and depressor reflexes arising from the jeopardized myocardium were suggested. Some link, though fragile, now existed between the laboratory and the complexitiy of human disease. I think that this link may be further sub- stantiated if the hemodynamic alterations that can accompany acute and reversible electrocardiographic changes typical of ischemic episodes of the myocardium are analyzed properly. It is possible to observe: (1)decreases in arterial pressure and heart rate (Guazzi et al. 1971); (2) a decrease in arterial pressure and a rise in heart rate (Guazzi et al. 1971, 1975;Maseri et al. 1978); (3) increases in arterial pressure and heart rate (Lewis 1931; Roughgarden 1966; Littler et al. 1973; Guazzi et al. 1975;Maseri et al. 1978). In some cases, it was clearly shown (Guazzi et al. 1971, 1975; Maseri et al. 1978; Figueras et al. 1979; Chierchia et al. 1980; Figueras and Cinca 1981) that hemodynamic and electrocardiographic alterations could precede pain or occur in the absence of it. Thus, the participation of vagally mediated depressor reflexes and of sympathetically mediated excitatory reflexes appears extremely likely (Fig. 30). More specifically, hypertension and tachycardia preceding or independent of pain would be the result of a reflex from the heart and not of a primary and undetermined "vasomotor storm" as hypothesized by Lewis ( 1931 ). It is obvious that a black box of fundamental importance embraces the fact that an increased sympathetic afferent activity can induce reflexes Cardiovascular Sympathetic Afferent Fibers 65

without pain or, less likely, pain without reflexes. The careful studies of Foreman and associates (Foreman et al. 1978;Foreman and Ohata 1980) attempt to face this problem. Yet, "'it must be remembered that there is a critical and still mysterious step between input of sensory origin to the higher central nervous system and conscious perception" (Perl 1971 ).

INPUT OUTPUT B RAI N STEM ~'~

V / /

SPINAL CORD

Fig. 30. Schema of the neural pathways mediating reflexes from the heart during myocardial ischemia. (From Malliani 1978)

Moreover, a pathophysiological event could also be that of an increased vagal and sympathetic efferent activity as the result of an excitation of both vagovagal and sympathosympathetic reflexes (Malliani et al. 1980). Such an event would weaken the old concept of vagal and sympathetic outflows working only in a sort of reciprocal arrangement. These neural mechanisms are likely to play a crucial role in life-threatening arrhythmias which may be associated with myocardial ischemia (Schwartz et al. 1975, 1978; Malliani and Lombardi 1978; Lown 1979; Malliani et al. 1980). A peculiar clinical example of an excitatory cardiovascular reflex mediated by sympathetic afferent fibers could be tt~at of hypertension after coronary bypass surgery (Tarazi et al. 1978; Estefanous and Tarazi 1980; Wallach et al. 1980) that was rapidly controlled with lidocaine block of one stellate ganglion (Tarazi et al. 1978). In brief, old and recent experimental studies on cardiovascular innervation have often opened new ways of interpreting the complexity of clinical reality. On the other hand, the recognition of this complexity should prevent any wish to generalize too much from any particular experimental model.

However, these are only notes from the initial pages of a travelogue. A conclusion should not even be attempted: "there will be time" (T.S. Eliot). 66 A. Malliani

References

Alexander RS (1945) The effects of blood flow and anoxia on spinal cardiovascular centers. Am J Physiol 143:698-708 Armour JA (1973) Physiological behavior of thoracic cardiovascular receptors. Am J Physiol 225:177-185 Aviado DM, Schmidt CF (1955) Reflexes from stretch receptors in blood vessels, heart and lungs. Physiol Rev 35:247-300 Bainbridge FA (1915) The influence of venous filling upon the rate of the heart. J Physiol (Lond) 50:65-84 Baker DG, Coleridge HM, Coleridge JCG, Nerdrum T (1980) Search for a cardiac noci- ceptor: stimulation by bradykinin of sympathetic afferent nerve endings in the heart of the cat. J Physiol (Lond) 306:519-536 Bard P (1960) Anatomical organization of the central nervous system in relation to control of the heart and blood vessels. Physiol Rev (Suppl) 40:3-26 Beacham WS, Kunze DL (1969) Renal receptors evoking a spinal vasomotor reflex. J Physiol (Lond) 201:73-85 Beacham WS, Perl ER (1964) Background and reflex discharge of sympathetic preganglionic neurones in the spinal cat. J Physiol (Lond) 172:400-416 Beccari E (1934) Contribution fi l'&ude de l'innervation sensibile pulmonaire et des r6flexes proprioceptifs respiratoires. Arch Int Physiol 39:257-294 Bergamaschi M, Longoni AM (1973) Cardiovascular events in anxiety: experimental studies in the conscious dog. Am Heart J 86:385-394 Berkley HJ (1894) The intrinsic nerve supply of cardiac ventricles in certain verte- brates. Johns Hopkins Hosp Rep 4:248-255 Bishop VS, Peterson DF (1978) The circulatory influences of vagal afferents at rest and during coronary occlusion in conscious dogs. Circulat Res 43:840-847 Bishop VS, Lombardi F, Malliani A, Pagani M, Recordati G (1976) Reflex sympathetic tachycardia during intravenous infusions in chronic spinal cats. Am J Physiol 230:25-29 Bosnjak ZK, Zuperku E J, Coon RL, Kampine JP (1979) Acute coronary artery occlusion and cardiac sympathetic afferent nerve activity. Proc Soc Exp Biol Med 161: 142-148 Bot~r J (1966) The autonomic nervous system. An introduction to its physiology and pathological histology. Akad6miai Kiad6, Budapest Bristow JD, Brown EW, Cunningham DJC et al. (1971) Effect of bicycling on the baroreflex regulation of pulse interval. Circulat Res 28:582-592 Bronk DW, Ferguson LK, Margaria R, Solandt DY (1936) The activity of the cardiac sympathetic centers. Am J Physiol 117:237-249 Brooks CM (1933) Reflex activation of the sympathetic system in the spinal cat. Am J Physiol 106:251-266 Brooks CM (1935) The reaction o£ chronic spinal animals to hemorrhage. Am J Physiol 114:30-39 Brown AM (1964) Afferent innervation of the coronary arteries and cardiac chambers. Ph.D. thesis, University of London Brown AM (1967) Excitation of afferent cardiac sympathetic nerve fibres during myocardial ischaemia. J Physiol (Lond) 190:35-53 Brown AM (1968) Motor innervation of the coronary arteries of the cat. J Physiol (Lond) 198:311-328 Brown AM (1979) Cardiac reflexes. In: Berne RM, Sperelakis N, Geiger SR (eds) Handbook of physiology. 2. The cardiovascular system, vol 1. The heart. American Physiological Society, Washington DC, pp 677-689 Brown AM, Malliani A (1971) Spinal sympathetic reflexes initiated by coronary receptors. J Physiol (Lond) 212:685-705 Cardiovascular Sympathetic Afferent Fibers 67

Burch GE, De Pasquale NP (1963) Bradykinin. Am Heart J 65 : 116-123 Burgess PR, Perl ER (1973) Cutaneous mechanoreceptors and nociceptors. In: Iggo A (ed) Handbook of sensory physiology, vol 2. Somatosensory system. Springer, Berlin Heidelberg New York, pp 29-78 Carpenter D, Engberg I, Lundberg A (1966) Primary afferent depolarization evoked from the brain stem and the cerebellum. Arch Ital Biol 104:73-81 Casati R, Lombardi F, Malliani A (1979) Afferent sympathetic unmyelinated fibres with left ventricular endings in cats. J Physiol (Lond) 292:135-148 Catton WT ( 1970) Mechanoreceptor function. Physiol Rev 50:297-318 Chierchia S, Brunelli C, Simonetti I, Lazzari M, Maseri A (1980) Sequence of events in angina at rest: primary reduction in coronary flow. Circulation 61:759-768 Coggeshall RE (1980) Law of separation of function of the spinal roots. Physiol Rev 60:716-755 Coggeshall RE, Galbraith SL (1978) Categories of axons in mammalian rami communicantes. II. J Comp Neurol 181:349-360 Coggeshall RE, Coulter JD, Willis WD (1974) Unmyelinated axons in the ventral roots of the cat lumbosacral enlargement. J Comp Neurol 153:39-58 Coleridge HM, Coleridge JCG (1980) Cardiovascular afferents involved in regulation of peripheral vessels. Annu Rev Physio142:413-427 Coleridge HM, Kidd C, Coleridge JCG, Banzett RB (1975)Multiterminal sympathetic afferent fibers supplying the thoracic organs of cats and dogs. Physiologist 18:173 Coleridge HM, Coleridge JCG, Kidd C (1978) Afferent innervation of the heart and great vessels: a comparison of the vagal and sympathetic components. Acta Physiol Pol (Suppl) 29:55-79 Coleridge JCG, Coleridge HM (1979) Chemoreflex regulation of the heart. In: Berne RM, Sperelakis N, Geiger SR (eds) Handbook of physiology. 2. The cardiovascular system, vol. 1 The heart. American Physiological Society, Washington DC, pp 653- 676 Coleridge JCG, Linden RJ (1955) The effect of intravenous infusions upon the heart rate of the anaesthetized dog. J Physiol (Lond) 128:310-319 Coleridge JCG, Hemingway A, Holmes RL, Linden RJ (1957) The location of atrial receptors in the dog: a physiological and histological study. J Physiol (Lond) 136: 174-197 Coote JH, Hilton SM, Perez-Gonzales JF (1971) The reflex nature of the pressor response to muscular exercise. J Physiol (Lond) 215:789-804 Corbett JL, Frankel HL, Harris PJ (1971a) Cardiovascular changes associated with skeletal muscle spasm in tetraplegic man. J Physiol (Lond) 215:381-393 Corbett JL, Frankel HL, Harris PJ (1971b) Cardiovascular reflex responses to cutaneous and visceral stimuli in spinal man. J Physiol (Lond) 215:395-409 Corbett JL, Frankel HL, Harris PJ (1971c) Cardiovascular responses to tilting in tetraplegic man. J Physiol (Lond) 215:411-431 Costantin LR (1963) Extracardiac factors contributing to hypotension during coronary occlusion.Am J Cardiol 11:205-217 Cyon E, Ludwig C (1866) Die Reflexe eines der sensiblen Nerven des Herzens auf die motorischen der Blutgef~isse. Ber Saechs Ges (Akad) Wiss 18:307-328 De Waele H, Van de Velde J (1940) Sur un r~flexe hypertenseur des oreillettes. Arch Int Physiol 50:33-53 Dogiel AS (1898) Die sensiblen Nervenendigungen im Herzen und in den Blutgef~issen tier S~iugethiere. Arch Mikrosk Anat 52:44-70 Dokukin AV (1964) Blood pressure and pulse changes in normal and vagotomized animals during acute myocardial ischemia. Fed Proc (Suppl) 23 :T583-586 Downman CBB, McSwiney BA (1946) Reflexes elicited by visceral stimulation in the acute spinal animal. J Physiol (Lond) 105:80-94 Edgeworth FH (1892) On a large-fibred sensory supply of the thoracic and abdominal viscera. J Physiol (Lond) 13:260-271 68 A. Malliani

Engberg I. Lundberg A, Ryall RW (1968a) Reticulospinal inhibition of transmission in reflex pathways. J Physiol (Lond) 194:201-223 Engberg I, Lundberg A, Ryall RW (1968b) Reticulospinal inhibition of interneurones. J Physiol (Lond) 194:225-236 Estefanous FG, Tarazi RC (1980) Systemic arterial hypertension associated with cardiac surgery. Am J Cardiol 46:685-694 Felder RB, Thames MD (1979) Interaction between cardiac receptors and sinoaortic baroreceptors in the control of efferent cardiac sympathetic nerve activity during myocardial ischemia in dogs. Circ Res 45:728-736 Felder RB, Thames MD (1981) The cardiocardiac sympathetic reflex during coronary occlusion in anesthetized dogs. Circ Res 48:685-692 Fernandez de Molina A, Perl ER (1965) Sympathetic activity and the systemic circulation in the spinal cat. J Physiol (Lond) 181:82-102 Figueras J, Cinca J (1981) Acute arterial hypertension during spontaneous angina in patients with fixed coronary stenosis and exertional angina: an associated rather than a triggering phenomenon. Circulation 64:60-68 Figueras J, Singh BN, Ganz W, Charuzi Y, Swan HJC (1979) Mechanism of rest and nocturnal angina: observations during continuous hemodynamic and electrocardiographic monito ring. Circulation 59:955 -968 Floyd K (1979) Light microscopy of nerve endings in the atrial endocardium. In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge University Press, Cambridge, pp 3-24 Foreman RD, Ohata CA (1980) Effects of coronary artery occlusion on thoracic spinal neurons receiving viscerosomatic inputs. Am J Physiol 238 :H667-H674 Foreman RD, Ohata CA, Gerhart KD (1978)Neural mechanisms underlying cardiac pain. In: Schwartz P J, Brown AM, Malliani A, Zanchetti A (eds) Neural mechanisms in cardiac arrhythmias. Raven Press, New York, pp 191-207 Franz DN, Evans MH, Perl ER (1966) Characteristics of viscerosympathetic reflexes in the spinal cat. Am J Physiol 211 : 1292-1298 Gaskell WH (1886) On the structure, distribution and function of the nerves which innervate the visceral and vascular systems. J Physiol (Lond) 7:1-80 Grundfest H (1966) Comparative electrobiology of excitable membranes. In: Ad- vances in comparative physiology and biochemistry, vol 2. Academic Press~ New York, pp 1-116 Guazzi M, Polese A, Fiorentini C, Magrini F, Bartorelli C (1971) Left ventricular performance and related haemodynamic changes in Prinzmetal's variant angina pectoris. Br Heart J 33:84-94 Guazzi M, Polese A, Fiorentini C, Magrini F, Olivari MT, Bartorelli C (1975) Left and right heart haemodynamics during spontaneous angina pectoris. Comparison between angina with ST segment depression and angina with ST segment elevation. Br Heart J 37:401-413 Gupta PD (1975) Spinal autonomic afferents in elicitation of tachycardia in volume infusion in the dog. Am J Physiot 229:303-308 Gupta PD, Singh M (1977) Autonomic afferents at T1 in elicitation of volume-induced tachycardia in the dog. Am J Physiol 232 :H464-H469 Guttmann L, Whitteridge D (1947) Effects of bladder distension on autonomic mechanisms after spinal cord injuries. Brain 70:361-404 Guzman F, Braun C, Lira RKS (1962) Visceral pain and the pseudoaffective response to intra-arterial injection of bradykinin and other algesic agents. Arch Int Pharmaco- dyn 136:353-483 Hainsworth R, Kidd C, Linden RJ (eds) (1979) Cardiac receptors. Cambridge Uni- versity Press, Cambridge Head H (1921) Release of function in the nervous system. Proc. R Soc Lond (Biol) 92:184-209 Cardiovascular Sympathetic Afferent Fibers 69

Hess GL, Zuperku E J, Coon RL, Kampine JP (1974) Sympathetic afferent nerve activity of left ventricular origin. Am J Physiol 227:543-546 Heymans C, Neil E (1958) Reflexogenic areas of the cardiovascular system. Churchill, London Heymans C, Bouckaert JJ, Farber S, Hsu FY (1936) Spinal vasomotor reflexes associated with variations in blood pressure. Am J Physiol 117:619-625 Hilton SM (1966) Hypothalamic regulation of the cardiovascular system. Br Med Bull 22:243 -248 Holmes R (1957a) Structures in the atrial endocardium of the dog which stain with methylene blue, and the effects of unilateral vagotomy. J Anat 91:259-266 Holmes RL (1957b) Cholinesterase activity in the atrial wall of the dog and cat heart. J Physiol (Lond) 137:421-426 Holmes R, Torrance RW (1959) Afferent fibres of the stellate ganglion. Q J Exp Physiol 44:271-281 Horwitz LD, Bishop VS (1972) Effect of acute volume loading on heart rate in the conscious dog. Circ Res 30: 316-321 Johnston BD (1968) Nerve endings in the human endocardium. Am J Anat 122:621- 629 Jones JJ (1962) The Bainbridge reflex. J Physiol (Lond) 160:298-305 Jonnesco T (1921) Traitement chirurgical de l'angine de poitrine par la rrsection du sympathique cervico-thoracique. Press M~d 29:193-194 Kaufman MP, Baker DG, Coleridge HM, Coleridge JCG (1980) Stimulation by bradykinin of afferent vagal C-fibers with chemosensitive endings in the heart and aorta of the dog. Circ Res 46:476-484 Khabarova AY (1963) The afferent innervation of the heart. Consultants Bureau, New York Khayutin VM, Baraz LA, Lukoshkova EV, Sonina RS, Chernilovskaya PE (1976) Chemosensitive spinal afferents: thresholds of specific and nociceptive reflexes as compared with thresholds of excitation for receptors and axons. In: Iggo A, Ilyinsky OB (eds) Progress in brain research, vol 43. Elsevier, Amsterdam, pp 293-306 Kostreva DR, Zuperku EJ, Purtock RV, Coon RL, Kampine JP (1975) Sympathetic afferent nerve activation of right heart origin. Am J Physiol 229:911-915 Kumada N, Nogami K, Sagawa K (1975) Modulation of carotid sinus baroreceptor reflex by sciatic nerve stimulation. Am J Physiol 228:1535-1541 Kuntz A (1945) Anatomic and physiologic properties of cutaneo-visceral vasomotor reflex arcs. J Neurophysiol 8:421-429 Langley JN (1896) Observations on the medullated fibres of the sympathetic system and chiefly on those of the grey rami communicantes. J Physiol (Lond) 20:55-76 Langley JN (1898) On the union of cranial autonomic (visceral) fibres with the nerve cells of the superior cervical ganglion. J Physiol (Lond) 23:240-270 Langley JN (1903) The autonomic nervous system. Brain 26:1-26 Langley JN (1915-1916) Sketch of the progress of discovery in the eighteenth century as regards the autonomic nervous system. J Physiol (Lond) 50:225-258 Langley JN (1924) Vaso-motor centres. Part III. Spinal vascular (and other autonomic) reflexes and the effect of strychnine on them. J Physiol (Lond) 59:231-258 Leek B F (1967) Abdominal and pelvic visceral receptors. Br Med Bull 33:163-168 Leriche R, Fontaine R (1927) The surgical treatment of angina pectoris. Am Heart J 3:649-671 Lewis T (1931) Angina pectoris associated with high blood pressure and its relief by amyl nitrite; with a note on Nothnagel's syndrome. Heart 15:305-327 Lewis T, Kellgren JH (1939-1942) Observations relating to referred pain, viscero- motor reflexes and other associated phenomena. Clin Sci 4:47-71 Linden RJ (1979) Atrial receptors and heart rate. In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge University Press, Cambridge, pp 165-190 70 A. Malliani

Lindgren I, Olivercrona H (1947) Surgical treatment of angina pectoris. J Neurosurg 4: 19-39 Lioy F, Szeto PM (1975) Baroreceptor and chemoreceptor influence on the cardiovascular responses initiated by stretch of the thoracic aorta. Physiologist 18:293 Lioy F, Malliani A, Pagani M, Recordati G, Schwartz PJ (1974) Reflex hemodynamic responses initiated from the thoracic aorta. Circ Res 34:78-84 Littler WA, Honour J, Sleight P, Stott FD (1973) Direct arterial pressure and electrocardiogram in unrestricted patients with angina pectoris. Circulation 48:125-134 Lombardi F, Malliani A, Pagani M (1976) Nervous activity of afferent sympathetic fibers innervating the pulmonary veins. Brain Res 113:197-200 Lombardi F, Della Bella P, Casalone C, Malfatto G, Malliani A (1981a) A sympathetic pressor reflex elicited by coronary occlusion in cats. In: 8th Congr Int Soc Hyper- tension, 31 st May-3rd June 1981. Ricerca Scientifica, suppl 19, Milan Lombardi F, Della Bella P, Casati R, Malliani A (1981b) Effects of intracoronary administration of bradykinin on the impulse activity of afferent sympathetic unmyelinated fibers with left ventricular endings in the cat. Circ Res 48:69- 75 Lombardi F, Patton CP, Della Bella P, Pagani M, Malliani A (1982) Cardiovascular and sympathetic responses reflexly elicited through the excitation with bradykinin of sympathetic and vagal cardiac sensory endings in the cat. Cardiovasc Res 16:57-65 Lown B (1979) Sudden cardiac death: the major challenge confronting contemporary cardiology. Am J Cardiol 43:313-328 Malliani A (1978) Nervous reflex mechanisms during acute myocardial ischemia. In: Maseri A, Klassen GA, Lesch M (eds) Primary and secondary angina pectoris. Grune & Stratton, New York, pp 329-333 Malliani A (1979) Afferent cardiovascular sympathetic nerve fibres and their function in the neural regulation of the circulation. In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge University Press, pp 319-338 Malliani A (1980) Disagreement on the reflex sympathetic activity elicited by experimental coronary occlusion. Circ Res 47:627-628 Malliani A (1981) Central and reflex regulation of the sympathetic nervous system and psychosomatic cardiovascular disorders. In: Kielholz P, Siegenthaler W, Taggart P, Zanchetti A (eds) Psychosomatic cardiovascular disorders - when and how to treat? Huber, Bern, pp 59-63 Malliani A, Brown AM (1970) Reflexes arising from coronary receptors. Brain Res 24: 352-355 Malliani A, Lombardi F (1978) Neural reflexes associated with myocardial ischemia. In: Schwartz PJ, Brown AM, Malliani A, Zanchetti A (eds) Neural mechanisms in cardiac arrhythmias. Raven Press, New York, pp 209-219 Malliani A, Lombardi F (1982) Consideration of the fundamental mechanisms eliciting cardiac pain. Am Heart J 103:575-578 Malliani A, Pagani M (1976) Afferent sympathetic nerve fibres with aortic endings. J Physiol (Lond) 263:157-169 Malliani A, Schwartz P J, Zanchetti A (1969a) Reflex activity of single preganglionic sympathetic fibres during coronary occlusion. Experientia 25:152-153 Malliani A, Schwartz P J, Zanchetti A (1969b) A sympathetic reflex elicited by experimental coronary occlusion. Am J Physiol 217:703-709 Malliani A, Pagani M, Recordati G, Schwartz PJ (1970) Evidence for a spinal sympathetic regulation of cardiovascular function. Experientia 26:965 -966 Malliani A, Pagani M, Recordati G, Schwartz PJ (197 l a) Spinal sympathetic reflexes elicited by increases in arterial blood pressure. Am J Physiol 220:128-134 Malliani A, Pagani M, Recordati G, Schwartz PJ (1971b) Sympathetic reflexes from the heart. In: Bartorelli C, Zanchetti A (eds) Cardiovascular regulation in health and disease. Cardiovascular Research Institute, Milan, pp 119-135 Cardiovascular Sympathetic Afferent Fibers 71

Malliani A, Peterson DF, Bishop VS, Brown AM (1972a) Spinal sympathetic cardiocardiac reflexes. Circ Res 30:158-166 Malliani A, Recordati G, Schwartz P J, Pagani M (1972b) Tonic afferent sympathetic activity from the heart. Experientia 28:269-270 Malliani A, Parks M, Tuckett RP, Brown AM (1973a) Reflex increases in heart rate elicited by stimulation of afferent cardiac sympathetic nerve fibers in the cat. Circ Res 32:9-14 Malliani A, Recordati G, Schwartz PJ (1973b) Nervous activity of afferent cardiac sympathetic fibres with atrial and ventricular endings. J Physiol (Lond) 229:457-469 Malliani A, Lombardi F, Pagani M, Recordati G, Schwartz PJ (1975a) Spinal cardiovascular reflexes. Brain Res 87:239-246 Malliani A, Lombardi F, Pagani M, Recordati G, Schwartz PJ (1975b) Spinal sympathetic reflexes in the cat and the pathogenesis of arterial hypertension. Clin Sci Mol Med 48:259s-260s Malliani A, Pagani M, Bergamaschi M (1979) Positive feedback sympathetic reflexes and hypertension. Am J Cardiol 44:860-865 Malliani A, Schwartz PJ, Zanchetti A (1980) Neural mechanisms in life-threatening arrhythmias. Am Heart J 100:705-715 Maseri A, Sever/S, De Nes Met al. (1978) Variant angina: one aspect of a continuous spectrum of vasospastic myocardial ischemia. Am J Cardiol 42:1019-1035 Meyling HA (1953) Structure and significance of the peripheral extension of the autonomic nervous system. J Comp Neurol 99:495-543 Miller MR, Kasahara M (1964) Studies on the nerve endings in the heart. Am J Anat 115:217-233 Mitchell GAG (1953) The innervation of the heart. Br Heart J 15:159-171 Mizeres NJ (1955) The anatomy of the autonomic nervous system in the dog. Am J Anat 96:285-318 Moruzzi G (1940) Paleocerebellar inhibition of vasomotor and respiratory carotid sinus reflexes. J Neurophysiol 3:20-32 Muratori G (1934) Connessioni tra tessuto paragangliare e zone recettrici aortiche in vari mammiferi. Monit Zool Ital 45:300-310 Murkherjee SR (1957) Effect of bladder distension on arterial blood pressure and renal circulation in acute spinal cats. J Physiol (Lond) 138:300-306 Neto FR, Brasil JCF, Antonio A (1974) Bradykinin induced coronary chemoreflex in the dog. Arch Exp Pathol Pharmakol 283 : 135-142 Nettleship WA (1936) Experimental studies on the afferent innervation of the cat's heart. J Comp Neurol 64:115-131 Nishi K, Sakanashi M, Takenaka F (1974) Afferent fibres from pulmonary arterial baroreceptors in the left cardiac sympathetic nerve of the cat. J Physiol (Lond) 240:53-66 Nishi K, Sakanashi M, Takenaka F (1977) Activation of afferent cardiac sympathetic nerve fibres of the cat by pain producing substances and by noxious heat. Pfluegers Arch 372:53-61 Nonidez JF (1939) Studies on the innervation of the heart. I. Distribution of the cardiac nerves, with special reference to the identification of the sympathetic and parasympathetic postganglionics. Am J Anat 65:361-413 Nonidez JF (1941) Studies on the innervation of the heart. II. Afferent nerve endings in the large arteries and veins. Am J Anat 68:151-189 Oldefield B J, McLachlan EM (1978) Localization of sensory neurons traversing the stellate ganglion of the cat. J Comp Neurol 182:915-922 Pagani M (1975) Afferent sympathetic nerve fibres with aortic endings. J Physiol (Lond) 252:45-46P Pagani M, Schwartz PJ, Banks R, Lombardi F, Malliani A (1974) Reflex responses of sympathetic preganglionic neurones initiated by different cardiovascular receptors in spinal animals. Brain Res 68:215-225 72 A. Malliani

Pagani M, Schwartz PJ, Bishop VS, Malliani A (1975) Reflex sympathetic changes in aortic diastolic pressure-diameter relationship. Am J Phyiol 229:286-290 Pagani M, Vatner SF, Baig H, Braunwald E (1978) Initial myocardial adjustments to brief periods of ischemia and reperfusion in the conscious dog. Circ Res 43:83-92 Pagani M, Mirsky I, Baig H, Manders WT, Kerkhof P, Vatner SF (1979) Effects of age on carotic pressure-diameter and elastic stiffness-stress relationships in unanesthetized sheep. Circ Res 44:420-429 Pagani M, Pizzinelli P, Furlan R, Guzzetti S, Malliani A (1980) Analysis of the sympathetic reflex initiated by aortic distension in conscious dogs. Circulation (Suppl) 62:150 Pagani M, Pizzinelli P, Furlan R, Guzzetti S, Rimoldi O, Malliani A (1981) A sympathetic hypertensive reflex from the heart of conscious dogs. Clin Sci 61 : 181 s-183s Pagani M, Pizzinelli P, Bergamaschi M, Malliani A (1982) A positive feedback sympathetic pressor reflex during stretch of the thoracic aorta in conscious dogs. Circ Res 50:125-132 Pannier R (1946) Contribution ~i l'innervation sympathique du coeur. Les nerfs cardio- acc61~rateurs. Arch Int Pharmacodyn 73:193-259 Pantridge JF (1978) Autonomic disturbance at the onset of acute myocardial infarction. In: Schwartz P J, Brown AM, Malliani A, Zanchetti A (eds) Neural mechanisms in cardiac arrhythmias. Raven Press, New York, pp 7-17 Perl ER (1971) Is pain a specific sensation? J Psychiatr Res 8:273-287 Peterson DF, Bishop VS (1974) Reflex blood pressure control during acute myocardial ischemia in l~he conscious dog. Circ Res 34:226-232 Peterson DF, Brown AM (1971) Pressor reflexes produced by stimulation of afferent cardiac nerve fibres in the cardiac sympathetic nerves of the cat. Circ Res 28: 605 -610 Peterson DF, Kaspar RL, Bishop VS (1973) Reflex tachycardia due to a temporary coronary occlusion in the conscious dog. Circ Res 32:652-659 Purtock RV, Von Colditz JH, Seagard JL, Igler FO, Zuperku E J, Kampine JP (1977) Reflex effects of thoracic sympathetic afferent nerve stimulation on the kidney. Am J Physiol 235 :H580-H586 Randall DC, Hasson DM, Brady JV (1978) Acute cardiovascular consequences of anterior descending coronary artery occlusion in unanesthetized monkey. Proc Soc Exp Biol Med 58:135-140 Randall WC, McNally H, Cowan J, Caliguiri L, Rohse WG (1957) Functional analysis of the cardioaugmentor and cardioaccelerator pathways in the dog. Am J Physiol 191:213-217 Ranson SW, Billingsley PR (1918a) The thoracic truncus sympathicus, rami communicantes and splanchnic nerves in the cat. J Comp Neuro129:405-439 Ranson SW, Bitlingsley PR (1918b) An experimental analysis of the sympathetic trunks and greater splanchnic nerve in the cat. J Comp Neurol 29:441-456 Recordati G, Schwartz PJ, Pagani M, Malliani A, Brown AM (1971) Activation of cardiac vagal receptors during myocardial ischemia. Experientia 27:1423-1424 Recordati G, Lombardi F, Bishop VS, Malliani A (1975) Response of type B atrial vagal receptors to changes in wall tension during atrial fining. Circ Res 36:682-691 Recordati G, Lombardi F, Bishop VS, Malliani A (1976) Mechanical stimuli exciting type A atrial vagal receptors in the cat. Circ Res 38:397-403 Reimann KA, Weaver LC (1980) Contrasting reflexes evoked by chemical activation of cardiac afferent nerves. Am J Physiol 239:H316-H325 Richins CA, Brizzee K (1949) Effect of localized cutaneous stimulation on circulation in duodenal arterioles and capillary beds. J Neurophysiol 12:131-136 Roughgarden JW (1966) Circulatory changes associated with spontaneous angina pectoris. Am J Med 41:947-961 Cardiovascular Sympathetic Afferent Fibers 73

Rushmer RF, Smith OA, Lasher EP (1960) Neural mechanisms of cardiac control during exertion. Physiol Rev (Suppl) 40:27-34 Salisbury PF, Cross CE, Rieben PA (1960) Reflex effects of left ventricular distension. Circ Res 8:530-534 Schwartz PJ,Pagani M, Lombardi F, MaUiani A, Brown AM (1973) A cardiocardiac sympathovagal reflex in the cat. Circ Res 32:215-220 Schwartz PJ, Periti M, Malliani A (1975) The long Q-T syndrome. Am Heart J 89: 378-390 Schwartz P J, Foreman RD, Stone HL, Brown AM (1976) Effect of dorsal root section on the arrhythmias associated with coro~nary occlusion. Am J Physiol 231:923-928 Schwartz P J, Brown AM, Malliani A, Zanchetti A (eds) (1978) Neural mechanisms in cardiac arrhythmias. Raven Press, New York Seagard JL, Pederson HJ, Kostreva DR, Van Horn DL, Cusik JF, Kampine JP (1978) Ultrastructural identification of afferent fibers of cardiac origin in thoracic sympathetic nerves in the dog. Am J Anat 153:217-232 Sherrington CS (1898) Decerebrate rigidity, and reflex coordination of movements. J Physiol (Lond) 22:319-332 Sherrington CS (1906) The integrative action of the nervous system. Yale University Press, New Haven Sleight P, Widdicombe JG (1965) Action potentials in afferent fibres from pericardial mechanoreceptors in the dog. J Physiol (Lond) 181:259-269 Smirnov A (1895) Ueber die sensiblen Nervenendigungen im Herzen bei Amphibien und S~iugetieren. Anat Anz 10:737-749 Smith OA (1974) Reflex and central mechanisms involved in the control of the heart and circulation. Annu Rev Physiol 36:93-123 Smyth HS, Sleight P, Picketing GW (1969) Reflex regulation of arterial pressure during sleep in man. Circ Res 24:109-121 Staszewska-Barczak J, Ferreira SH, Vane JR (1976) An excitatory nociceptive cardiac reflex elicited by bradykinin and potentiated by prostaglandins and myocardial ischaemia. Cardiovasc Res 10:314-327 Staszewska-Barczak, J, Dusting GJ (1977) Sympathetic cardiovascular reflex initiated by bradykinin-induced stimulation of cardiac pain receptors in the dog. Clin Exp Pharmacol Physiol 4:443-452 Sutton DC, Lueth HC (1930) Experimental production of pain on excitation of the heart and great vessels. Arch Intern Med 45:827-867 Takeshita A, Matsuguchi H, Nakamura M (1980) Effect of coronary occlusion on arterial baroreflex control of heart rate. Cardiovasc Res 14:303-306 Taquini AC, Aviado DM (1961) Reflex stimulation of heart induced by partial occlusion of pulmonary artery. Am J Physiol 200:647-650 Tarazi RC, Estefanous FG, Fouad FM (1978) Unilateral steUate block in the treatment of hypertension after coronary by-pass surgery. Impfications of a new therapeutic approach. Am J Cardio142 :1013-1018 Thor~n P (1979) Role of cardiac vagal C-fibers in cardiovascular control. Rev Physiol Biochem Pharmacol 86:1-94 Tranum-Jensen J (1975) The ultrastructure of the sensory end-organs (baroreceptors) in the atrial endocardium of young mini-pigs. J Anat 119:255-275 Uchida Y (1975a) Afferent sympathetic nerve fibers with mechanoreceptors in the right heart. Am J Physiol 228:223-230 Uchida Y (1975b) Afferent aortic nerve fibers with their pathways in cardiac sympathetic nerves. Am J Physio1228 :990-995 Uchida Y, Murao S (1974a) Potassium-induced excitation of afferent cardiac sympathetic nerve fibers. Am J Physiol 226:603-607 Uchida Y, Murao S (1974b) Excitation of afferent cardiac sympathetic nerve fibers during coronary occlusion. Am J Physiol 226:1094-1099 74 A. Malliani: Cardiovascular Sympathetic Afferent Fibers

Uchida Y, Murao S (1974c) Afferent sympathetic nerve fibers originating in the left atrial wall. Am J Physiol 227:753-758 Uchida Y, Murao S (1974d) Bradykinin-induced excitation of afferent cardiac sympathetic nerve fibers. Jpn Heart J 15:84-91 Uchida Y, Murao S (1975) Acid-induced excitation of afferent cardiac sympathetic nerve fibers. Am J Physiol 228:27-33 Uchida Y, Kamisaka K, Murao S, Ueda H (1974) Mechanosensitivity of afferent cardiac sympathetic nerve fibers. Am J Physiol 226:1088-1093 Ueda H, Uchida Y, Kamisaka K (1969) Distribution and responses of the cardiac sym- patheticreceptorsto mechanically induced circulatory changes. Jpn Heart J 10:70-81 Vatner SF, Pagani M (1976) Cardiovascular adjustments to exercise: hemodynamics and mechanisms. Prog Cardiovasc Dis 89:91 - 108 Vatner ST, Boettcher DH, Heindrickx GR, McRitchie RJ (1975) Reduced baroreflex sensitivity with volume loading in conscious dogs. Circ Res 37:236-242 Von Bezold A, Hirt L (1867) Ueber die physiologischen Wirkungen des essigsauren Veratrins. Untersuch Physiol Lab Wtirzburg 1:73-156 Wall PD (1976) Modulation of pain by nonpainful events. In: Bonica J J, Albe-Fessard D (eds) Advances in pain research and therapy, vol 1. Raven Press, New York, pp 1-16 Wallach R, Karp RB, Reves JG, Oparil S, Smith LR, James TN (1980) Pathogenesis of paroxysmal hypertension developing during and after coronary bypass surgery: a study of hemodynamic and humoral factors. Am J Cardiol 46:559-565 Weaver LC (1977) Cardiopulmonary sympathetic afferent influences on renal nerve activity. Am J Physiol 233 :H592-H599 Weaver LC, Danos LM, Oehl RS, Meckler RL (1981) Contrasting reflex influences of cardiac afferent nerves during coronary occlusion. Am J Physiol 240:H620-H629 Webb SW, Adgey AA, Pantridge JF (1972) Autonomic disturbance at onset of acute myocardial infarction. Br Med J 3:89-92 White JC (1957) Cardiac pain. Anatomic pathways and physiologic mechanisms. Circulation 16:644-655 Williams TH (1964) Mitral and tricuspid valve innervation. Br Heart J 26:105-115 Wollard HH (1926) The innervation of the heart. J Anat 60:345-373 Woodsworth RS, Sherrington CS (1904) A pseudoaffective reflex and its spinal path. J Physiol (Lond) 31:234-243 Rev. Physiol. Biochem. Pharmacol., Vol. 94 © by Springer Verlag 1982

The Functions of the Renal Nerves

GERALD F. DIBONA*

Contents 1 Introduction ...... 76 2 Renal Neuroanatomy ...... 76 2.1 Gross Innervation ...... 77 2.2 Intrinsic Innervation ...... 77 2.3 Catecholamine Receptors ...... 81 2.4 Catecholamine Metabolism ...... 83 2.5 Summary ...... 86 3 Electrical Characteristics of the Renal Nerves ...... 87 3.1 Efferent Renal Nerves ...... 87 3.2 Afferent Renal Nerves ...... 96 3.3 Summary ...... 98 4 Physiological Functions of the Renal Nerves ...... 99 4.1 Control of the Renal Circulation ...... 99 4.2 Control of Renal Tubular Solute and Water Transport ...... 107 4.2.1 Renal Denervation ...... 107 4.2.2 Direct Electrical Renal Nerve Stimulation ...... 116 4.2.3 Reflex Alterations in Efferent Renal Sympathetic Nerve Activity... 121 4.2.4 Characterization of Catecholamine Receptors ...... 131 4.2.5 Summary ...... '_.34 4.3 Control of Renal Hormonal Systems ...... 135 4.3.1 Renin ...... 135 4.3.1.1 Direct Stimulation of the Renal Nerves ...... 135 4.3.1.2 Reflex Stimulation of the Renal Nerves ...... 135 4.3.1.3 Role of/3-Adrenoceptors in the Neural Control of Renin Release . . . 138 4.3.1.4 Role of ~-Adrenoceptors in the Neural Control of Renal Release . . . 140 4.3.1.5 Role of Prostaglandins in Neural Control of Renal Release ...... 142 4.1.3.6 Integrated Aspects of the Neural Control of Renal Release ...... 145 4.3.2 Prostaglandin ...... 147 4.3.3 Kallikrein ...... 147 4.4 Renorenal Reflexes ...... 147 4.5 Hypertension ...... 152 4.6 Summary ...... 155 5 Concluding Remarks ...... 156 References ...... 157

Professor and Vice Chairman, Department of Internal Medicine, University of Iowa College of Medicine and Chief, Medical Service, Veterans Administration Medical Center, Iowa City, Iowa 52242, USA 76 G.F. DiBona

1 Introduction

The structure and function of the intrinsic innervation of the kidney have been investigated for over 100 years. Until recently, there has been no agreement concerning the precise anatomical distribution or neurotransmitter specificity of the renal nerves. Recently, combination electron microscopic, histochemical, and fluorescent methods have more precisely localized the distribution and neurotransmitter specificity of the nerves within the kidney. Up until the time of these anatomical studies, the physiological role of the renal nerves was a subject of much controversy. Much of the controversy existed because previous experiments involved stressful anesthesia and/or surgery, the comparison of an innervated kidney with a possibly incompletely denervated kidney, or the use of high levels of direct electrical renal nerve stimulation as opposed to physiological reflex alterations in efferent renal nerve activity. To summarize the views of one authority, adamant in his view that the renal nerves were unimportant in the regulation of renal excretory function under normal conditions, "For the mo- ment it may be said that substantial evidence of the neural control of either the tubular excretion or reabsorption of any urinary constituent is lacking." (Smith 1937). Since these early observations our understanding of the physiological role of the intrinsic renal innervation has advanced to a more sophisticated level. It is the purpose of this survey to critically review and summarize the current state of information concerning the functions of the renal nerves. In view of several recently published reviews (Gill 1969;Pogglitseh 1973; Schrier 1974; Hillemand et al. 1976; DiBona 1977, 1978, 1981; Gottsehalk et al. 1978; Linden 1978; Gottsehalk 1979; Gill 1979; Kim et al. 1979) which address many portions of this topic, only selected aspects will be discussed.

2 Renal Neuroanatomy

The innervation of the kidney has been a subject of intense study since Pappenheim's early observation that nerve fibers enter the kidney together with the main renal artery and run along it down to its finest branches (Pappenheim 1840). The Functions of the Renal Nerves 77

2.1 Gross Innervation

Relative to its size, the kidney has a richer innervation than almost any other organ (Mitchell 1950). The status of knowledge in this area is represented by the work of Mitchell (1950), DeMuyMer (1952), and Shvalev (1966). The renal nerves are described as being composed of fibers derived from the celiac plexus, the thoracic and lumbar branches of the splanchnic nerves, the superior and inferior mesenteric plexus, the intermesenteric nerves, and the superior hypogastric plexus (Mitchell 1950). Based on spinal cord stimulation studies (Takeuchi et al. 1964) these fibers derive from spinal cord segments Ts to L3. All of these nerve fibers and their interconnections make up the renal plexus which lies in rather constant association with the aorticorenal ganglion. The aorticorenal ganglion is the largest ganglion associated with the renal plexus and lies near the junction of the aorta and the renal artery (Norvell 1968). The renal nerve fibers that enter the kidney derive from the renal plexus and course along the renal artery and vein to enter the hilus.

2.2 Intrinsic Innervation

The introduction of specific histochemical and fluorescent techniques for the identification of adrenergic and cholinergic neurons and the application of electron microscopy has greatly clarified the details of the distribution and neurotransmitter specificity of the intrinsic renal innervation. The conclusions of the older literature (Mitchell 1950; DeMuylder 1952) were that the renal nerves, both adrenergic and cholinergic, were distributed to the blood vessels of the kidney but did not innervate renal tubular structures. However, the elegant series of studies by Bara]as and colleagues pro- vides clear evidence that these conclusions must be revised. Using a combination of catecholamine fluorescent histochemistry and autoradiography for localization of exogenous tritiated norepinephrine for demonstration of adrenergic nerves, the thiocholine histochemical method for demonstration of acetylcholinesterase-containing nerves, and electron microscopy, Bara]as and colleagues (reviewed in 1978) have studied the intrinsic renal innervation in the rat and monkey. In both the rat and monkey, prominent adrenergic nerve bundles are associated with the arterioles in the cortex, characteristically appearing in the space between the afferent and efferent glomerular arterioles and the surrounding tubules. Nerve bundles are seen adjacent to the tubules, often filling the space between it and the arteriole. The tubules receive a distinct tubular innervation with the finding of nerve bundels closely following the contour of both proximal and distal tubules; 78 G.F. DiBona

these tubular branches arise from the periarteriolar nerves. This pattern of distribution is similar in the monkey and the rat but the nerve bundles are thinner and the density of innervation is less in the rat than in the monkey. Electron microscopy discloses in both rat and monkey that the nerves are composed of variable numbers of axons partially or totally surrounded by a Schwann cell. The axons display dilated segments (varicosities) which contain mitochondria and the characteristic vesicles observed in autonomic nerves (small dense-cored vesicles, neurosecretory granules). The varicosities establish contact with both arteriolar walls and tubular epithelial cells. At the site of contact the basement membranes of the nerve and arteriolar wall or tubular epithelial cell fuse and this site is referred to as a nerve terminal (neuroeffector junction). In both proximal and distal tubules, varicosities containing small dense-cored vesicles are seen in direct contact with the tubular epithelial cell basement membrane. In the rat, light and electron microscopic autoradiography was used for localization of exogenous tritiated norepinephrine (Bara]as and Wang 1979). Accumulation of grains were noted in axonal varicosities packed with small, dense-cored vesicles, which were in direct contact with afferent and efferent arterioles, juxtaglomerular granular cells, and proximal and distal tubules. Neuroeffector junctions were characterized by a space of 150-250 nm in width separating the plasma membrane of the effector cell from that of the axolemma; basement membrane material was present in this space. Using similar techniques in the dog, DiBona (1977) has shown that proximal and distal tubular epithelial cells are directly innervated by catecholamine-containing adrenergic nerve terminals. Using electron microscopy alone, Zimrnerman (1972) observed in 13-16 week old human fetuses that the distal convoluted tubule was innervated; he demonstrated nerve terminals containing small dense-cored vesicles in direct contact with the basement membranes of distal tubular epithelial cells. Neural innervation of renal tubules has been demonstrated in non- mammalian species. Pang et al. (1982) have demonstrated nerve terminals in contact with renal tubular epithelial cells of the bullfrog, Rana cates- beiana. With regard to cholinergic nerves, the studies of Bara]as and colleagues (1974, 1975, 1976) have led to a revised understanding of this matter. Acetylcholinesterase-containing nerve bundles are associated with the afferent and efferent glomerular arterioles and both proximal and distal tubules. Since the specific histochemical precipitate reflecting acetylcholinesterase, copper ferrocyanide, is electron opaque, the light microscopic histochemical findings can be verified with the electron microscope. In both monkey and rat, acetylcholinesterase deposits are located extracellu- larly around axons and varicosities in the perivascular and peritubular The Functions of the Renal Nerves 79 nerves. However, little or no acetylcholinesterase deposit is seen at the neuroeffector junctions. The histochemical demonstration of acetylcholinesterase in renal nerves has long been considered to indicate the existence of a distinct cholinergic innervation. Such a view was supported by the presence of residual acetylcholinesterase innervation after the disappearance of adrenergic fluorescence following renal transplantation (Weitsen and Norvell 1969; Norvell et al. 1970). However, two observations suggested that the acetylcholinesterase-positive nerves might really be adrenergic and contain the enzyme. First, in the rat, serial section electron microscopy showed small dense-cored vesicles characteristic of adrenergic nerves in all axon segments present in the juxtaglomerular region, an area where acetylcholinesterase-positive nerves are abundant. Second, in the monkey, electron microscopy shows that all nerve bundles around the glomerular arterioles have acetylcholinesterase deposits while, by catecholamine fluorescence histochemistry, a dense adrenergic innervation is characteristic of that region. To test this hypothesis further, Bara]as and Wang (1975) used the agent 6-hydroxydopamine which selectively destroys adrenergic nerves. If the acetylcholinesterase-positive nerves are adrenergic but contain the enzyme, administration of 6-hydroxydopamine should result in the disappearance of both acetylcholinesterase and catecholamine fluorescence from the nerves. In the rat, administration of 6-hydroxydopamine resulted in the disappearance of acetylcholinesterase and catecholamine fluorescence from virtually all nerves associated with the glomerular arterioles and the adjacent tubules. However, there was slight residual acetylcholinesterase and catecholamine fluorescence seen in association with small arteries and larger blood vessels elsewhere in the kidney. Elec- tron microscopy disclosed degeneration of the nerves associated with the glomerular arterioles and the adjacent tubules. These studies support the presence of an exclusive adrenergic innervation of the glomerular arterioles and the adjacent tubules with the presence of acetylcholinesterase in adrenergic nerves being in accord with the hypothesis of Burn and Rand (1965). It is known that the overwhelming majority of spinal viscerosensory fibers are myelinated fibers of large (over 7 pm) and medium (4-7 pro) diameter and that the kidney of dog and man contains the smallest number of such sensory fibers in comparison (ascending order) to small intestine, liver, lungs, and heart. Zimmerman (1975) and Bara]as. and Wang (1978) demonstrated that the rat kidney contains myelinated and unmyelinated nerve fibers. They observed nerve bundles with myelinated and unmyelinated axons in three areas of the kidney: the corticomedullary region at the outer stripe of the outer zone of the medulla, the periarterial loose connective tissue, and the subepithelial connective tissue of the calyces. The diameter of 17 myelinated axons averaged 2.8 pm (range, 2.1-3.9 80 G.F. DiBona

/~m) and the diameter of 180 unmyelinated axons averaged 0.5/am (range, 0.1-1.3 gm). The results of light and electron microscopic autoradiography for the localization of exogenous tritiated norepinephrine indicated that the unmyelinated nerve fibers are adrenergic. Niifima (1975)has shown that the rabbit renal nerve trunk contains myelinated nerve fibers with an average diameter of 4.3 ~m (range, 2.0-8.0 t~m, 166 fibers); parallel physiological studies indicated that these myelinated nerve fibers were afferent. Thus, these observations suggest that there is a close functional relationship in the kidney between the afferent myelinated and the efferent adrenergic unmyelinated nerve fibers. The innervation of the juxtaglomerular apparatus (rat) has been recently reviewed by Gorgas (1978a, b) and Barajas (1979, 1981). Fluorescent histochemistry for biogenic amines demonstrates a plexus of catechol- aminergic nerves associated with the glomerular arterioles extending from the afferent to the efferent arteriole and the adjacent tubules. Electron microscopy discloses the presence in the nerves of small dense-cored vesicles thought to contain norepinephrine and believed to be characteristic of adrenergic nerves. Their disappearance after the injection of reserpine correlates with the depletion of catecholamines from the renal tissue and the abolition of catecholamine fluorescence. Serial section electron microscopy indicates that about one-fourth of the cells of the vascular component and about one-third of the cells of the afferent and efferent arterioles are innervated. Only one-tenth of the cells in the extraglomerular mesangial region were innervated while about half of the granular cells in the glomerular arterioles and one-sixth of the granular cells (lacis and smooth muscle cells) of the vascular component were innervated. Although based on evaluation of a single juxtaglomerular apparatus, it would appear that a large proportion of the cells of the vascular component are non- innervated. Of particular importance is the observation that axons can be in contact with both vascular and tubular cells; thus, the same axon can innervate granular cells, smooth muscle cells in the glomerular arterioles, and cells of the distal tubule. This ultrastructural finding makes plausible the suggestion that the activity of a single axon could affect the function of the juxtaglomerular apparatus by having a direct effect on renin secretion from the juxtaglomerular granular cells, by changing the diameter of the arterioles through a direct action on vascular smooth muscle cells, and by a direct action on epithelial cells of the distal tubule near the macula densa. The serial section technique disclosed that all axons contained small dense-cored vesicles which are characteristic of adrenergic nerves. Thus, this observation suggests that the innervation of the juxtaglomerular region is exclusively adrenergic. Further support for the exclusive adrenergic innervation of the juxtaglomerular apparatus is derived from the studies with 6-hydroxy-dop- The Functions of the Renal Nerves 81

amine (vide supra). Treatment with 6-hydroxydopamine resulted in almost total disappearance of both catecholamine fluorescence and acetylcholinesterase activity from the juxtaglomerular apparatus. Electron microscopy showed degenerating axons. Since 6-hydroxydopamine destroys only adrenergic nerve endings, this finding supports the hypothesis that the majority of the nerves in the juxtaglomerular apparatus are adrenergic nerves which contain acetylcholinesterase. Additional evidence for sole adrenergic innervation of the juxtaglomerular apparatus comes from studies using the uptake of tritiated norepinephrine as a specific functional marker for adrenergic nerves (Bara]as and Wang 1979). Light and electron microscopic autoradiography showed accumulations of grains in association with afferent and efferent arterioles as well as adjacent proximal and distal tubules. The grains were also noted to be in contact with juxtaglomerular granular cells. Virtually all of the grains were on axons in varicosities packed with vesicles, some of which were of the small dense-cored variety. Thus, these findings support the hypothesis that the juxtaglomerular apparatus is innervated mainly by adrenergic nerves.

2.3 Catecholamine Receptors

The subject of renal catecholamine receptors has recently been reviewed by Insel and Snavely (1981). Using a fluorescent /~-adrenoceptor antagonist, 9-amino-acridine-propranolol, Atlas et al. (1977) demonstrated localization in the epithelium of proximal and distal convoluted tubules and collecting ducts as well as the efferent arterioles of the glomerular vascular pole and the juxtaglomerular apparatus. Further detailed localization was not possible and the blockade of fluorescence with propranolol was equivocal. Young and Kuhar (1980) reported that ~-2 adrenoceptors are located predominantly on the proximal tubules of the guinea pig kidney. They used an in vivo labeling autoradiographic technique to examine the distribution of specific [3H] clonidine binding sites with the light microscope. However, the process of identification of the proximal tubule was not rigorous and depended entirely on poorly defined anatomical criteria. Bind- ing of [3H] WB-4101, an ~-1 adrenoceptor antagonist, was not observed. Radioligand binding techniques have been used to identify renal adrenoceptors in partially purified renal tubular plasma membrane preparations. For ~-adrenoceptors, radioligand binding has been used to identify ~-2 adrenoceptors in the guinea pig kidney (Jarrott et al. 1979) and both ~-1 and ~-2 adrenoceptors in the rat kidney (Rouot and Snyder 1979; U'PrichardandSnyder 1979). In addition, Graham et al. (1978, 1980) have reported that renal ~-adrenoceptors are increased in spontaneously 82 G.F. DiBona hypertensive rats and stroke-prone spontaneously hypertensive rats as compared to normotensive Wistar-Kyoto control rats. FeMer et al. (1980a) found renal tubular a-adrenoceptors in the rat but not the dog kidney. Pettinger et al. (1981) showed that total a-adrenoceptor number was higher in renal membranes from kidneys of Dahl sodium-sensitive rats than Dahl sodium-resistant rats and increased further with a high sodium diet. Increased a-2 adrenoceptor binding accounted for most of the incre- ment, although a-1 adrenoceptor binding was also increased. High sodium diet did not affect a-1 or a-2 adrenoceptor binding in Dahl sodium-reistant rats. Binding affinities were not affected. Information on the effect of alterations in dietary sodium intake on adrenoceptors in normal rat renal membranes is required in order to interpret these changes in a mixed genetic-environmental form of experimental hypertension. For /3-adrenoceptors, radioligand binding has been used to identify renal ~-adrenoceptors in the rat kidney (Woodcock et al. 1978; Eliahou et al. 1980; Gavendo et al. 1980; Snavely and Insel 1980). Gavendo et al. (1980) demonstrated that the order of potency for inhibition of radioligand binding of /3-adrenoceptor antagonists was isoproterenol > epinephrine ~> norepinephrine, thus being consistent with a/3-1 adrenoceptor (Hoffman and Lefkowitz 1980). Felder et al. (1980a) found renal tubular ~-adrenoceptors in both the rat and dog kidney. With respect to the classification and quantitation of/3-adrenoceptor subtypes (Minneman et al. 1981), the hypothesis of Carlsson et al. (1972) must be considered. This hypothesis suggests that both/3-1 and ~-2 adrenoceptors could coexist in the same organ and be involved in many /3-adrenoceptor-mediated responses. The relative involvement of the two/~-adrenoceptor subtypes will vary depending on the agonist involved and the relative amounts of the two /3-adrenoceptor subtypes existing in the effector organ under study. For dopaminergic receptors,Dinerstein et al. (1979) used histofluorescence techniques to demonstrate neuronal elements at the glomerular vascular poles of dog renal cortex containing predominantly dopamine. A prelim- inery report indicates the existence of dopamine receptors in dog (Scott and Vanderwende 1980) and rat (Felder et al. 1980b, 1981) renal cortex (Adam 1980). Glomerular adrenoceptors have been sought in dogs and rats. a- and t3-adrenoceptors have been found in the glomeruli of the dog and rat (Felder et al. 1980a). Dopamine receptors have been found in the glomeruli and tubules of the rat kidney (Felder et al. 1980b, 1981). Although these represent important initial investigations, the ability of these studies to provide precise anatomical localization of these receptors is limited since the preparations employed contain material from multiple cell types and different tubular segments. Further work will be necessary before it will be possible to completely define renal tubular epithelial cell The Functions of the Renal Nerves 83 catecholamine receptor anatomy, e.g., luminal versus peritubular membrane, proximal convoluted versus proximal straight segments, superficial versus juxtamedullary, and cortex versus medulla.

2.4 Catecholamine Metabolism

The renal metabolism of catecholamines in relation to activation of efferent renal sympathetic nerves and urinary sodium excretion has been studied extensively by Baines, Morgunov, and colleagues (Morgunov 1980). Using microinjection techniques, it was demonstrated that after rat proximal tubular injection of norepinephrine, dopamine, normetanephrine, or methoxytyramine, 87%-94% was recovered in the urine of the injected kidney. Less than 10% was chemically altered during passage through the nephron. After peritubular capillary injection, first passage tubular secretion was 25% for dopamine, 47% for methoxytyramine, 13% for norepinephrine, and 4% for normetanephrine. After peritubular capillary injections of dopamine, urinary excretion of methoxytyramine and dopamine was greater from the microinjected than the contralateral kidneys, whereas after peritubular capillary injection of norepinephrine, urinary excretion of norepinephrine and normetanephrine was similar from the two kidneys. Thus, dopamine and norepinephrine released into peritubular capillaries are methylated by catechol-O-methyl-transferase and both amines and their methylated derivates are secreted into the tubular lumen with nearly complete delivery into the final urine (Baines et al. 1979). The fate of catecholamines which diffuse into peritubular cortical interstitial space has been examined using subcapsular microinjection of radioactive catecholamines. Fractional secretion rates were 20% for norepinephrine, 47% for epinephrine, and 66% for dopamine, and were not affected by prior chronic renal denervation. Increasing circulating plasma dopamine concentrations inhibited the tubular secretion of norepinephrine and dopamine (Baines and Morgunov 1980). Urinary catecholamine excretion may derive from several sources: filtration, reabsorption, and secretion of catecholamines entering the kidney in renal artery blood; release from renal nerve endings; and production by nonneuronal sources in the kidney. Measuring catecholamine concentrations in arterial blood, renal vein blood, lymph, and urine from innervated and denervated kidneys in the same rat, Baines and colleagues have derived several important quantitative conclusions. For urinary norepinephrine excretion, approximately 30% derives from circulating norepinephrine with the remainder derived from the renal nerves since renal denervation reduced the renal component of urinary norepinephrine excretion to zero. For urinary epinephrine excretion, approximately 70% derives from circulating epinephrine with the 84 G.F. DiBona

remainder derived from the renal nerves, since renal denervation reduced the renal component of urinary epinephrine excretion to zero. For urinary dopamine excretion, none is derived from circulating dopamine and all is derived approximately equally from the renal nerves and nonneuronal sources in the kidney (Stephenson et al. 1982). In general, renal denervation decreases renal venous concentrations of norepinephrine, epinephrine, and dopamine to levels below those observed in arterial blood. Under control conditions, renal lymph concentrations of all three catecholamines are in the range of arterial and renal venous catecholamine concentrations. Following activation of efferent renal sympathetic nerves, rena] lymph concentrations are higher for norepinephrine, lower for epinephrine, and approximately the same for dopamine in comparison to paired arterial blood samples (Baines and Morgunov 1980). Since the low circulating arterial concentration of free dopamine cannot explain the rate of urinary dopamine excretion, Baines and Chan (1980) demonstrated that as much as 30% of urinary dopamine excretion could derive from the metabolism by renal nonneuronal tissue of circulating free L-dihydroxyphenylalanine (L-dopa). It is known that both innervated and denervated kidneys contain L-dopa decarboxylase, the enzyme responsible for conversion of L- dopa to dopamine, presumably in nonneuronal tissue such as renal tubular epithelial cells (Nagatsu et al. 1969). Using bilateral common carotid artery occlusion to reflexly increase efferent renal sympathetic nerve activity (RSNA), Morgunov and Baines ( 1981 a) have shown that the increase in urinary norepinephrine excretion derives from both systemic extrarenal sources and the renal nerves. The increase in urinary epinephrine excretion derives from systemic extrarenal sources with little contribution from the renal nerves and the increase in urinary dopamine excretion derives exclusively from the renal nerves with no systemic extrarenal contribution. In the rabbit Lappe et al. (1980a) and Willis et al. (1980) reported that norepinephrine released from nerve terminals by renal nerve stimulation and 3H-norepinephrine (renal cortical application) released from postglomerular nerve terminals by tyramine administration were exreted into the urine by a cationic tubular secretory process which was inhibited by cyanine but not by probenecid. In regard to the relationship between the renal regulation of extracellular fluid volume and urinary catecholamine excretion, it is known that increases in dietary sodium intake lead to duration-dependent increases in extracellular fluid volume with a constant plasma sodium concentration (Reinhardt and Behrenbeck 1967; Kaezmarezyk et al. 1979). A direct correlation between sodium intake and urinary dopamine excretion and an inverse one with urinary norepinephrine excretion have been described (Alexander et al. 1974; Oates et al. 1979). However, Baines and Morgunov The Functions of the Renal Nerves 85

(1980) have shown that increased dietary sodium intake increases the urinary excretion of both norepinephrine and dopamine in rats. Compari- son studies studies with isotonic glucose or sodium bicarbonate solution as drinking fluid indicate that urinary flow rate, urinary pH (Reynolds et al. 1978), and dietary carbohydrate intake (DeHaven et al. 1980) as well as sodium intake modify urinary catecholamine excretion. In the bilateral common carotid artery occlusion studies of Morgunov and Baines (1981), referred to earlier, a low dietary sodium intake reduced the systemic extrarenal contribution but not the renal nerve contribution to a lowered urinary excretion of norepinephrine, enhanced the systemic extrarenal contribution but not the renal nerve contribution to an increased urinary excretion of epinephrine, and reduced the systemic extrarenal contribution but not the renal contribution to a decreased urinary excretion of dopamine. A high dietary sodium intake reduced the systemic extrarenal contribution and abolished the renal contribution to a reduced urinary excretion of norepinephrine and abolished both the systemic extrarenal and renal release of epinephrine and dopamine. Thus, the urinary excretion of catecholamines derived from renal nerves was markedly influenced by dietary sodium intake. Angiotensin II, known to be elevated during dietary sodium deprivation (Fray et al. 1977), potentiates the release of catecholamines from nerve endings (Zimmerman 1978; Westfall 1980). However, dietary sodium deprivation also results in loss of catecholamines from peripheral nerve endings with a resultant decreased ability to respond to acute stimulation (L]ungqvist 1975; Rocehini et al. 1977). Dietary sodium excess may decrease catecholamine release from nerve endings via decreases in circulating angiotensin II concentrations. Additionally, volume expansion may modulate baroreceptor reflex responses through interaction via cardiopulmonary receptors (Clement et al. 1972). Also, baroreceptors are known to possess ionic (sodium) sensitivity (Brown 1980). Thus, multiple mechanisms activated by changes in dietary sodium intake may be involved in the observed alterations in renal catecholamine metabolism. In acute renal denervation experiments, the ipsilateral natriuresis was associated with a decrease in the urinary excretion of norepinephrine and and increase in the urinary excretion of dopamine. The contralateral antinatriuresis was associated with an increase in the urinary excretion of norepinephrine and a decrease in the urinary excretion of dopamine (Morgu- nov and Baines 1981a). Using direct electrical stimulation of the afferent vagus nerve, it was shown that the observed natriuresis was associated with an increase in the renal nerve-mediated release of dopamine but not norepinephrine; neither arterial pressure nor glomerular filtration rate were changed (Morgunov and Baines 1981 b). As discussed later (see Sect. 4.2), the relationship between endogenous dopamine and renal tubular sodium reabsorption remains unclear. 86 G.F. DiBona

The effect of direct electrical renal nerve stimulation on the release of catecholamines from the kidney into the renal venous blood or urine has been studied. Lappe et al. (1980b), using a level of renal nerve stimulation that reduced glomerular filtration rate by 30% in anesthetized rabbits, observed that the urinary excretion of norepinephrine but not epinephrine increased when factored for glomerular filtration rate. Since plasma norepinephrine concentration did not change, the urinary clearance ratio for norepinephrine was also increased by renal nerve stimulation. Kopp et al. (1980b) showed that the renal release rates of norepinephrine, epinephrine, and dopamine were negative in the acutely denervated kidney of the anesthetized dog. Stimulation of the renal nerves sufficient to reduce renal blood flow by 5% increased the renal release rate of norepinephrine from - 0.89 + 0.49 to 1.92 + 0.72 pmol/min per gram without any change in the renal release rate of epinephrine or dopamine. Stimulation of the renal nerves sufficient to reduce renal blood flow by 50% increased the renal release rate of norepinephrine from - 0.86 + 0.17 to 8.68 + 0.10 pmol/min per gram, and that of dopamine from - 0.15 + 0.04 to 0.33 + 0.04 pmol/ min per gram; it did not affect the renal release rate of epinephrine. Phen- oxybenzamine increased the renal release rates of both norepinephrine and dopamine during strong renal nerve stimulation, whereas both metoprolol and indomethacin had no effect. Oliver and colleagues (1980a) have shown that the renal release rate of norepinephrine is positive in the innervated kidney of both anesthetized and conscious dogs. There was a linear relationship between the frequency of renal nerve stimulation and the renal release rate of norepinephrine over the range of 0.5-18.0 Hz; however, the maximum reduction in renal blood flow occurred at 6.0 Hz.

2.5 Summary

Morphological studies indicate that the mammalian kidney receives a predominant adrenergic innervation which involves the vessels, tubules, and juxtaglomerutar apparatus. There is no evidence for a significant cholinergic innervation. Initial observations support the existence of dopaminergic neurons. Efferent unmyelinated nerve fibers predominate over afferent myelinated nerve fibers. Radioligand binding studies indicate that both glomeruli and tubules possess a- and ~-adrenoceptors as well as dopamine receptors. Direct or reflex-induced increases in efferent RSNA increase the release of norepinephrine and dopamine, but not epinephrine, into renal venous blood and urine. These responses are modified by alterations in dietary sodium intake. The kidney is able to synthesize dopamine from precursors in nonneuronal tissue. The Functions of the Renal Nerves 87

3 Electrical Characteristics of the Renal Nerves

This section will emphasize those investigations which have employed neurophysiological recording techniques to measure renal nerve activity directly. Those investigations in which alterations in renal nerve activity have been inferred from renal functional measurements are considered in Sect. 4.

3.1 Efferent Renal Nerves

Adrian, Bronk, and Phillips (1932) first demonstrated in the rabbit and cat that efferent renal sympathetic nerve activity (RSNA) occurred in pulse-synchronous rhythmic bursts with respiratory-dependent periodic variations of the nerve impulse frequency. A similar stiuation is known to exist in several other mammalian species, including the rat (Judy et al. 1971; Thoren and Ricksten 1979; Ricksten et al. 1979), cat (Engelhorn 1957), rabbit (Aars and Akre 1968), and dog (Takeuchi et al. 1965). In addition to these observations made in unconscious anesthetized animals, similar findings have been made in conscious unanesthetized animals (Judy et al. 1976; Ricksten et al. 1981; Weidinger and Kirchner 1967; Schad and Seller 1975; Kirchheirn and Gross 1978; Gross and Kirchheim 1980). Efferent RSNA is influenced by several reflex mechanisms. Carotid baroreceptor stimulation, i.e., increased carotid sinus pressure, inhibits both spontaneous and reflex efferent RSNA, while the reverse, i.e., decreased carotid sinus pressure, increases efferent RSNA (Kezdi and Geller 1968; Kirchheim and Gross 1978; Gross and Kirchheim 1980). There are multiple types and locations of cardiac mechanoreceptors and chemosensitive receptors, some of which have been shown to influence efferent RSNA (Thoren 1979; Coleridge and Coleridge 1980; Donald and Shepherd 1980). All four cardiac chambers contain receptors with myelinated vagal afferents, receptors with unmyelinated vagal afferents, and receptors with sympathetic (myelinated and unmyelinated) afferents. It would appear that receptors with myelinated vagal afferents are more numerous in the atria than in the ventricles, while the ventricular receptors with unmyelinated vagal afferents are more numerous in the left ventricle than in the right ventricle. Receptors with sympathetic afferents appear to be more numerous in the ventricles than in the atria. Investigations concerning the role of these various receptor groups in reflexly modulating efferent RSNA have employed various techniques to stimulate the receptors. They range from discrete stimulation (e.g., direct 88 G.F. DiBona

probing, small balloon inflation) to more widespread but local stimulation (e.g., left atrial balloon inflation, coronary artery occlusion, epicardial application of pharmacological agents) to more diffuse circulatory stimuli (e.g., volume expansion, hemorrhage, water immersion). In addition, the degree to which afferent input from other receptor areas influences the response of the receptor area under study is quite variable. Furthermore, the variety of efferent renal nerve recording techniques ranging from single fiber to few multifiber to whole nerve is an additional variable. Thus, these multiple considerations make it difficult to give an unambiguous description of these various control systems. Karim et al. (1972) demonstrated that relatively discrete activation of canine left atrial receptors by distension of balloons at the left pulmonary vein-atrial junction produced a mean decrease in impulse frequency of 27% in efferent RSNA; the response was abolished by cooling or section of both cervical vagi. This response was specific for the kidney since simultaneously measured cardiac sympathetic nerve activity increased while there was no change in lumbar or splenic sympathetic nerve activity. This response was not influenced by alterations in carotid sinus pressure (Lin- den et al. 1979) and was shown to be dependent only on atrial receptors discharging into myelinated vagal fibers (Linden et al. 1980). Prosnitz and DiBona (1978) showed that more widespread activation of canine left

AP mmHg

0 ~- t I I rain

LAP 2O mmHg 10 3°f0 ~-

Instantaneous 100 Frequency 50 Hz 0

VAGI INTACT VAGOTOMY ,ntegrated

Voltage rnV , dJ]__~/

Fig. I. Effect of left atrial balloon inflation on efferent renal sympathetic nerve activity in the anesthetized dog. AP, arterial pressure; LAP, ]eft atria] pressure. (Prosnitz and DiBona ]978) The Functions of the Renal Nerves 89 atrial receptors by left atrial balloon inflation produced a mean decrease in impulse frequency of 40% in efferent RSNA; this response was abolished by section of both cervical vagi (Fig. 1). Thus, these several studies indicate that left atrial receptor stimulation, independent of afferent input from carotid sinus baroreceptors, reflexly decreases efferent RSNA via an afferent pathway consisting of myelinated vagal fibers. Other workers have measured efferent RSNA following more nonspec- ific stimulation of receptors in the cardiopulmonary region subserved by vagal afferents. Clement et al. (1972) showed that 10% expansion of the blood volume in sinoaortic denervated rabbits reduced efferent RSNA by 41%; withdrawal of the blood volume returned efferent RSNA to the control level. A similar decrease in blood volume increased efferent RSNA by 33%; restoration of the blood volume returned efferent RSNA to the control level. These changes were unaffected by cutting the vagi at the diaphragm but were abolished by cutting the vagi in the neck. Interruption of vagal afferents resulted in an increase in efferent RSNA, indicating that vagal afferents exert a tonic inhibition on the sympathetic outflow to the kidney. These experiments demonstrate a role for the low pressure cardiopulmonary receptors (precise location indeterminate) in the control of efferent RSNA in response to changes in blood volume. Maneia et al. (1973), in dogs with aortic nerves cut and input from the carotid baroreceptors minimized by vascular isolation and perfusion of the carotid sinuses at 40 mmHg, demonstrated that cold block or section of the cervical vagi increased efferent RSNA by 28%. Cooling of the cervical vagi with carotid sinus pressure at 200 mmHg resulted in no change in efferent RSNA. In anesthetized sinoaortic denervated dogs Thames et al. (1980b) have shown that blood volume expansion produces a dose-dependent increase in left atrial pressure and a decrease in efferent RSNA which show a significant inverse linear correlation; the inhibition of efferent RSNA was enhanced by circumflex coronary artery injection of acetylstrophanthidin and abolished by vagotomy. Thus, cardiopulmonary receptors (precise location indeterminate) with afferent vagal fibers exert a tonic restraint on efferent RSNA, especially when input from the carotid and aortic baroreceptors is decreased or eliminated. In consideration of the interaction between low and high pressure baroreceptor reflexes in the control of efferent RSNA and the regulation of blood volume, several studies have been performed in which the major intervention is an acute change in blood volume, Echtenkamp et al. (1980), in the anesthetized nonhuman primate Macaea faseicularis, demonstrated that bolus intravenous volume expansion increased left atrial pressure and decreased efferent RSNA. The inhibition of efferent RSNA was partially abolished by vagotomy and totally abolished by a combination of vagotomy and sinoaortic denervation. Similar results were obtained 90 G.F. DiBona in the anesthetized cat (Echtenkamp and Gilmore 1980). In both the monkey and the cat, following vagotomy and sinoaortic denervation, there was no change in efferent RSNA following the administration of norepinephrine, intravascular volume expansion, or veratrine to stimulate intravascular mechanoreceptors. Similar results have been observed in the dog (Zucker et al. 1981). Thus, these observations indicate that there are no afferent pathways mediating intravascular mechanoreceptor modulation of efferent RSNA outside the carotid sinus, aortic and vagus nerves. These findings, which agree with those of Clement et al. (1972) in the rabbit, exclude a role for sympathetic afferent fibers and thus do not agree with the studies of Weaver et al. (1977, 1979) in the cat. Weaver (1977), in the anesthetized cat subjected to baroreceptor denervation and vagotomy, found that blood volume expansion produced a decrease in efferent RSNA which was correlated with the increase in central venous pressure. This response was abolished by thoracic sympathectomy. This difference in results was postulated to be time dependent in that it is possible that sympathetic afferent pathways may eventually compensate for lost baroreceptor and vagal pathways; however, their physiological role in the intact animal would be small. Ricksten et al. (1979), in sinoaortic denervated rats, showed that plasma volume expansion produced a decrease in efferent RSNA that was correlated with the increase in mean left atrial pressure. Bilateral vagotomy restored renal nerve activity to pre-plasma volume expansion levels. Aortic constriction produced a rise in mean left atrial pressure in association with a decrease in mean arterial pressure and efferent RSNA; bilateral vagotomy prevented decrease in efferent RSNA. These several studies indicate that low pressure cardiopulmonary receptors, located in the left side of the heart, with vagal afferent fibers participate in the control of efferent RSNA in response to changes in intravascular volume. The role of cardiopulmonary sympathetic afferents in reflexly influencing efferent RSNA has been studied in some detail. Weaver (1977), in the sinoaortic denervated and vagotomized cat, showed that electrical activation of cardiopulmonary sympathetic afferent nerves decreased (low frequency, 1-3 Hz) or increased (high frequency, 5-20 Hz) efferent RSNA. Purtoek et al. (1977) further demonstrated that sympathetic afferent fibers from cardiopulmonary receptors can modulate efferent RSNA during hypotension. Dogs were subjected to a constant pressure hemorrhage technique to lower mean arterial pressure to 50 mmHg; this produced stimulation of efferent RSNA via constant stimulation to the arterial baroreceptors. In agreement with the findings of Weaver (1977), low frequency (3 Hz) stimulation of cardiopulmonary sympathetic afferents decreased efferent RSNA, while high frequency (30 Hz) stimulation increased it. In a subsequent study, Weaver et al. (1979) explored further The Functions of the Renal Nerves 91 the ability of the cardiopulmonary sympathetic afferent nerves to both excite and inhibit efferent RSNA. The hypothesis that this was due to opposite responses of individual renal neurons to afferent stimulation was rejected because virtually all single postganglionic renal fibers responded to electrical cardiopulmonary sympathetic afferent stimulation with excitation followed by inhibition of discharge. The hypothesis that different cardiopulmonary sympathetic afferent neurons have opposite influences on renal nerve activity was confirmed when it was demonstrated in vagotomized cats that sympathetic afferent fibers activated by stretch of the right or left ventricle or aorta caused reflex excitation of renal nerve activity, whereas activation of sympathetic afferent fibers from the pulmonary vasculature by intravascular volume expansion or pressure increase caused an inhibition of this discharge. Stretch of the right or left atrium produced no change in renal nerve activity. Thus, the complexity of cardiopulmonary sympathetic afferent influences on efferent RSNA is due to hetero- geneity within the afferent rather than the efferent neural population. Kampine and colleagues (1980) have recently summarized their studies on the role of cardiopulmonary reflexes in the regulation of efferent RSNA. Lung inflation decreased efferent RSNA via activation of pulmonary stretch receptors with vagal afferents; lesser components derived from sympathetic afferents within the lung and chest wall receptors. Rapid increases in pulmonary arterial pressure decreased efferent RSNA via vagal afferent pathways. Rapid increases in chamber volume or pressure in all four cardiac chambers decreased efferent RSNA via vagal afferent pathways. They concluded that activation of cardiopulmonary afferents may decrease effferent RSNA; receptors with vagal afferent pathways predominate over receptors with sympathetic afferent pathways. There is evidence that both cardiac receptors with vagal afferents and sympathetic afferents are activated by coronary occlusion and chemical stimuli (Thoren 1979; Uchida 1979; Coleridge and Coleridge 1980). Thames and Abboud (1979a) examined the response to coronary occlusion (left anterior descending, LAD = anterior-lateral left ventricle; circumflex, Cx = inferoposterior left ventricle) in dogs with only carotid or with sinoaortic baroreceptors operative. LAD occlusion produced a small decrease in mean arterial pressure and a 24% increase in efferent RSNA, while Cx occlusion produced a greater decrease in mean arterial pressure and no change in efferent RSNA. The changes in left atrial pressure after LAD and Cx occlusion were similar. In carotid sinus or sinoaortic denervated dogs, coronary occlusions resulted in decreases in mean arterial pressure and efferent RSNA which were consistently greater during Cx occlusion than during LAD occlusion. These responses were abolished by vagotomy and enhanced by circumflex coronary artery injection of acetylstrophanthidin (Thames et al. 1980b). Waickman and Abboud (1980) have shown 92 G.F. DiBona

that activation of cardiac afferent nerves during coronary occlusion may prevent the compensatory reflex increase in sympathetic nerve activity seen during arterial hypotension. In anesthetized dogs with sectioned aortic nerves and isolated perfused carotid sinuses, reduction in carotid sinus pressure produced an increase in efferent RSNA which was the same in the absence and presence of LAD occlusion, whereas the response was markedly suppressed in the presence of Cx occlusion. These studies demonstrate that Cx occlusion and, to a lesser degree, LAD occlusion result in reflex inhibition of efferent RSNA mediated by left ventricular receptors with vagal afferents preferentially distributed in the inferoposterior left ventricular wall. Thames (1979) has also shown that left ventricular epicardial application or circumflex coronary artery injection of acetylstrophanthidin produced decreases in mean arterial pressure (25 mmHg), heart rate (10 beats/rain), and efferent RSNA (5.6 Hz or 40%) which were blocked by vagotomy. Weaver and Reimann (1979) showed in sinoaortic denervated cats that Cx occlusion inhibited efferent RSNA and that this effect was abolished by vagotomy. Conversely, LAD or right coronary artery occlusion produced excitation of efferent RSNA. In a further study, Weaver et al. (1981) showed that cardiac sympathetic afferent nerves can have excitatory influences on efferent RSNA during myocardial ischemia (coronary occlusion) that oppose inhibitory influences originating from vagally innervated cardiac receptors. These cardiac sympathetic afferent neurons can also contribute to the support of arterial pressure or the genesis of hypertension in this condition. Epicardial or intracoronary administration of bradykinin or potassium chloride increased mean arterial pressure and efferent RSNA in vagotomized, sinoaortic, denervated cats (mediated by cardiopulmonary sympathetic afferents), decreased mean arterial pressure and efferent RSNA in sinoaortic, cardiopulmonary sympathetic afferent denervated cats (mediated by vagal afferents), and produced increases, decreases, or no change in efferent RSNA in cats with only sinoaortic denervation or total innervation intact (Reimann and Weaver 1980). Felder and Thames (1980) have shown that bradykinin application to left ventricular myocardium can lead to both increases and decreases in efferent RSNA in sinoaortic, denervated, vagotomized dogs. These observations suggest that coronary occlusion with myocardial ischemia and possible attendant changes in the chemical milieu of cardiac receptors (Reimann and Weaver 1980; Coleridge and Coleridge 1980) can chemically activate cardiopulmonary sympathetic afferent neurons which are able to significantly alter mean arterial pressure and efferent RSNA despite the opposition of other vascular and cardiac afferent neurons. Volume expansion is known to decrease efferent RSNA. In anesthetized dogs with a 50% increase in blood volume produced by an acute The Functions of the Renal Nerves 93

isotonic saline load, Judy et al. (1971) demonstrated a reduction in efferent RSNA to 23% of the control value which persisted after mean arterial pressure returned to control level and was inversely correlated with the natriuresis and diuresis. In anesthetized, sinoarotic, denervated rabbits with a 10% increase or decrease in blood volume (dextran infusion or hemorrhage), Clement et al. (1972) observed that changes in efferent RSNA were inversely correlated with alterations in blood volume: expan- sions decreased efferent RSNA by 41% while depletion increased efferent RSNA by 33%. The effect on efferent RSNA was reversible and abolished by bilateral vagotomy in the neck but not at the diaphragm. Interruption of vagal afferents caused a 21% increase in basal efferent RSNA, indicating that the vagal afferents exert a tonic inhibition of efferent RSNA. In unanesthetized, conscious cats with intact or denervated sinoaortic baroreceptors, Sehad and Seller (1976) showed that 11% blood volume expansion decreased efferent RSNA by 48%; no differences were noted between animals with intact and denervated sinoaortic baroreceptors. Reeordati and Spielman (1977) demonstrated that isotonic saline volume expansion decreased efferent RSNA by 30%-50% in normal rats, in sinoaortic, denervated plus vagotomized rats, and in vagotomized plus spinal rats. All three groups showed bradycardia with increases in right atrial and mean arterial pressure. Visceral afferent stimulation (bladder distention) increased efferent RSNA. These results suggest that efferent RSNA may be modified by activation of visceral afferent input to the spinal cord and indicate a possible role for spinal sympathetic reflexes in the control of renal function. In anesthetized rats given a 5% body weight acute isotonic saline load, Kottra et al. (1978) reported that efferent RSNA decreased by 50% within 10-15 min after the start of the infusion and remained decreased by 30%-40% for the ensuing 45 min; mean arterial pressure was unchanged and the degree of natriuresis and diuresis appeared to correlate with the depression of efferent RSNA. Ricksten et al. (1981) have shown that intravenous isotonic saline volume expansion decreases efferent RSNA in conscious unanesthetized rats (Fig. 2). Thus, volume expansion decreases efferent RSNA in several mammalian species, both anesthetized and unanesthetized. These observations are consistent with the view that low pressure cardiopulmonary baroreceptors with vagal afferents participate in the control of efferent RSNA in response to acute changes in blood volume. Ferrario and colleagues have shown that dietary sodium deprivation decreases the reflex pressor response to carotid sinus hypotension (Brosni- han et al. 1978) and decreases the reflex responses of efferent RSNA to changes in mean arterial pressure (Takeshita and Ferrario 1980). This blunting was abolished following bilateral cervical vagotomy, implicating the buffering effects of either aortic or vagal afferent receptors on efferent RSNA in sodium-deprived dogs. 94 G.F. DiBona 2oo[

F .' i i i~;i;:~[il;i;;l~ii;lil;;ii~l;lIL;~Ll~ai~iiIl[;llii~iii r :;:J~[~hli:I,:l;;i:;;;;;;;i,iri;iilli,,,il;ilzi[ml,,L~r,:~lh;:;~;i~ ' ' ! , i .;::J:J,:lJ::...,:,:,:, ;:~,,.,~,t,,:,,I ...... I I r , I I I o~ Time,min T

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z ev t Volume expansion started Fig. 2. Effect of intravenous isotonic saline volume expansion (VE) in the conscious rat. AP, arterial pressure, MRAP, mean right atrial pressure; MAP, mean arterial pressure; RNA, renal nerve activity. (Ricksten et al. 1981)

Somatic, visceral, chemosensitive, and other afferents are known to exert an effect on efferent RSNA. Fedina and colleagues (1966) showed in anesthetized cats that single shock stimulation of the afferent limb of tibial or mesenteric nerve produced a reflex discharge and subsequently an inhibition of efferent RSNA. The inhibition was related to impulses of fast-conducting A fibers while, if sufficient stimulation intensity is used for exciting the afferent C fibers, a second reflex discharge follows the initial one. Pelletier and Shepherd (1975a), in vagotomized dogs, showed that stimulation of skeletal muscle receptors with capsaicin increased efferent RSNA by 111% over the maximum level recorded when carotid sinus pressure was 40 mmHg. The same workers (Pelletier and Shepherd 1975b) showed that the effect of hypoxia on efferent RSNA was small during the control state but was larger by 56% during bilateral carotid occlusion. In the anesthetized carotid sinus denervated dog, Whitwarn et al. (1979) showed that stimulation of the afferent limb of cutaneous nerves elicited two reflex discharges in efferent RSNA, whereas stimulation of the afferent limb of muscular nerves elicited the earlier but not the later of the reflex discharges in efferent RSNA. In anesthetized cats, Ninorniya and Fu]ita (1976) observed that efferent RSNA was little affected by changing skin temperature whereas changes in hypothalamic temperature elicited larger changes in efferent RSNA. In anesthetized cats, Ninomiya et al. (1974) showed that sinusoidal increases in intestinal pressure with a The Functions of the Renal Nerves 95 maximal amplitude of 20 cm H20 increased efferent RSNA by only 7%, whereas the increase in intestinal nerve activity was 107%. They concluded that reflex excitation by intestinal mechanoreceptor inputs through the sympathetic system is greater in intestinal nerves than in renal nerves. Nii]irna (1976), in anesthetized rabbits, showed that portal vein occlusion or elevation of mesenteric venous pressure produced a decrease in efferent RSNA that was similar to that produced by stimulation of the central part of a cut mesenteric branch of the splanchnic nerve; none of these responses was affected by a bilateral cervical vagotomy. It was suggested that mechanoreceptors in the mesenteric vein have reflex inhibitory input on efferent RSNA. Kostreva et al. (1980) showed, in dogs, that hepatic baroreceptor activation produced reflex increases in efferent RSNA that were eliminated by section of the anterior hepatic nerves. It was suggested that this hepatorenal reflex might be an important reflex mechanism that becomes activated during congestive heart failure and cirrhosis of the liver. Stimula- tion of the decentralized stellate ganglion decreases efferent RSNA (Takeuchi et al. 1968;Prosnitz andDiBona 1978) and this is abolished by carotid sinus denervation (Prosnitz and DiBona 1978). Thus, multiple afferent inputs from a wide variety of receptors with responses to different stimuli can influence efferent RSNA. Multiple pharmacological agents are known to produce alterations in efferent RSNA. As exemplified by the study of Aars (1972) in the anesthetized rabbit, a-adrenoceptor antagonists (phenoxybenzamine) produce a reflex inhibition of efferent RSNA despite a fall in mean arterial pressure. Similar observations have been reported with clonidine in anesthetized, vagotomized, sinoaortic, denervated cats by McCall and Gebber (1976); these studies indicated a possible activation by clonidine of central components of the baroreceptor reflex known to decrease efferent RSNA. Similarly, /3-adrenoceptor antagonists, both nonselective propranolol (Friggi et al. 1977a) and ~-1 selective atenolol (Friggi et al. 1977b), decrease efferent RSNA in the anesthetized rabbit despite decreases in mean arterial pressure. In the anesthetized cat, 1-(4-oxyphenyl)-2n-butylamino- ethanone hydrochloride (BON) markedly inhibits efferent RSNA (Fedina et al. 1970) in the resting state and the reflex response to bilateral carotid occlusion, acetylcholine-induced hypotension, asphyxia, or stimulation of somatic afferents. In anesthetized cats intravenous administration of L- dopa (Watanabe et al. 1974) or 5-hydroxytryptophan (Baum and Shrop- shire 1975) with an extracerebral decarboxylase inhibitor to prevent peripheral conversion of L-dopa to catecholamines results in a decrease in mean arterial pressure, heart rate, and efferent RSNA. This response is probably produced by an increase in central nervous system catecholamines since the hypotensive effect of L-dopa is accompanied by a concomitant accumulation of catecholamines in the brain. In support of a 96 G.F. DiBona spinal action of L-dopa to decrease efferent RSNA, similar observations were made in unanesthetized decerebrate cats (C1 cord section) by Coote and MeCleod (1974). Administration of dopamine, norepinephrine (Baum and Shropshire 1973), 5-hydroxytryptophan, and 5-hydroxytryptamine (Baum and Shropshire 1975) into the cerebral ventricle decreases efferent RSNA in anesthetized cats. Another pharmacological agent which modulates efferent RSNA, possibly by a central nervous system effect, is angiotensin II. Aars and Akre (1968), in the anesthetized rabbit, showed that angiotensin II infusion initially produced a decrease in the normal rhythmic pulse-synchronous efferent RSNA but then produced a nonrhythmic increase in efferent RSNA associated with a further increase in mean arterial pressure. This latter response was not related to changes in baroreceptor (aortic nerve) activity and could not be attributed to stimulation of chemoreceptors or sympathetic ganglia; an effect on central sympathetic neurons was postulated. Ferrario et al. (1976) showed, in anesthetized dogs, that vertebral artery infusion of angiotensin II produced a pressor response in association with an increase in splanchnic preganglionic nerve activity and a decrease in efferent RSNA. Whether the renal response was the result of selectively altered central control or was a reflex response secondary to baroreceptor activation was clarified by the experiments of Fukiyama (1972). Vertebral artery infusion of angiotensin II in anesthetized dogs produced a rise in mean arterial pressure and an initial increase in splanchnic preganglionic nerve activity and in efferent RSNA. During the sustained rise in mean arterial pressure, the rhythmic pulse-synchronous discharge in the efferent renal nerve disappeared completely and was replaced by nonrhythmic activity while the increase in splanchnic nerve activity was sustained. Thus, multiple pharmacological agents with a wide spectrum of cardiovascular and renal actions can influence efferent RSNA. The subject of spinal and supraspinal regulation of sympathetic nervous discharge, central nervous system organization and control of the baroreceptor reflex, and regulation of vascular resistance has been extensively reviewed recently and will not be dealt with further (Gebber 1980; Spyer 1981 ;Hilton and Spyer 1980).

3.2 Afferent Renal Nerves

Action potentials initiated by the activation of sensory nerve endings in the kidney have been recorded from the afferent renal nerves (Ueda and Uchida 1968) of rats (Astrom and Crafoord 1967;Recordati et al. 1978), cats (Pines 1960, 1966; Astrom and Crafoord 1968; Beacharn and Kunze 1969; Kady 1974; Calaresu et al. 1978), dogs (Ueda et al. 1967, 1971; The Functions of the Renal Nerves 97

MAP 200 I mmHg 100 0 t-

Left 80 1 L Ureteral Pressure 40 mmHg ~'~ 0 instantaneous I__50~RF I I r I ! I t f .eq°eee. r i r illllliltlILLi,l,i;Li4r ! !, , !T I lill ~ S i ,i ~ lll/it!lldlJiijlli.,v i di~ HZ 0 L ...... " ......

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Uchida et al. 1971 ;Kady 1974;Francisco et al. 1980), and rabbits (Nii]ima 1971, 1972a, b, 1975). These renal receptors respond to changes in intrarenal pressure as produced by alterations in renal artery pressure, renal vein occlusion, ureteral occlusion, or compression of the kidney and have been termed renal mechanoreceptors (Fig. 3). Other receptors, termed renal chemoceptive receptors, have been described by Recordati et al. (1978, 1980b) who have classified them into two groups in the rat. The R1 renal chemoceptive receptors are activated by renal ischemia as produced by renal artery occlusion, systemic hypotension, renal vein occlusion, or systemic asphyxia (Recordati et al. 1978). The R2 renal chemoceptive receptors are activated by alterations in the chemical environment of the renal interstitium as produced by changes in the excretory function of the kidney, the passage of ions from the renal pelivs across the pelvic epithelium (backflow of nondiuretic urine into the renal pelvis) (Recordati et al. 1980b), and injection of substances normally present in the urine into the renal artery of the cat (Pines 1969). The responses of these renal chemoceptive receptors are independent of changes in pelvic or intrarenal pressure. Thus, the renal nerves contain multiple afferent fibers which carry impulses centrally from renal receptors of different varieties and specificities. Ciriello and Calaresu (1980) have studied the central projections of afferent renal nerve fibers in the cat. Stimulation of afferent renal nerves evoked responses bilaterally in the paramedian reticular nucleus and lateral tegmental field of the medulla and in the lateral preoptic nucleus, 98 G.F. DiBona the lateral hypothalamus, and the paraventricular nucleus of the hypothalamus. Fifty-seven percent of the medullary units and 74% of the hypothalamic units also responded to afferent carotid sinus nerve stimulation. Similar central projections have been described for rat renal afferent nerve fibers (Knuepfer et al. 1980). Thus, renal afferent information is relayed to well-defined regions of the medulla and hypothalamus presumably involved in cardiovascular regulation and body sodium and water balance. A large proportion of these units show convergence of inputs from afferent renal nerve and afferent carotid sinus nerve fibers.

3.3 Summary

As can be seen from even a cursory review of the many published reports in this area, there are multiple pathways whereby efferent RSNA may be altered. It is not yet precisely understood whether summation or interaction exists between the effects of simultaneous activation of multiple different receptors on efferent RSNA. Additionally, the influence of concomitant changes in variables that can elicit known or unknown compensatory responses has not been rigorously defined. These several qualifica- tions make it difficult to attribute changes in efferent RSNA to a well- defined isolated reflex involving one type of receptor. Nevertheless, the available information allows some general conclusions concerning interventions which are known to produce substantial and consistent alterations in net efferent RSNA. Left atrial receptor stimulation produces a reflex decrease in efferent RSNA which is mediated by atrial receptors subserved by afferent vagal myelinated fibers. Receptors with vagal afferent fibers exert a tonic inhibitory restraint on efferent RSNA which is more pronounced when afferent input from the carotid and aortic baroreceptors is minimized. Studies involving acute increases in blood volume, with increases in left atrial and mean arterial pressure, produce reflex decreases in efferent RSNA which are largely dependent on vagal afferent fibers; the remainder of the afferent input derives from receptors subserved by the sinoaortic nerves. A role for receptors subserved by cardiopulmonary sympathetic afferent fibers in the response of efferent RSNA to volume expansion, coronary artery occlusion (myocardial ischemia), or intracoronary/epicardial administration of pharmacological agents has been proposed, but further investigation is required to define more clearly a physiological role for these pathways. Multiple other afferents (somatic, visceral, chemosensitive) as well as diverse pharmacological agents exert effects on efferent RSNA; their role in modulating physiologically important responses is less well understood. Although experiments involving the isolation and stimulation of a single receptor type, in the absence of con- The Functions of the Renal Nerves 99 comitant or compensatory responses involving other receptor mechanisms, are important for the definition of a reflex pathway, it is apparent that under most physiological conditions the alteration in efferent RSNA is a net response to a stimulus which involves multiple receptor mechanisms. Renal receptors, both mechanoreceptors and chemoceptive receptors, which when stimulated produce increases in afferent renal nerve activity and have central projections, have been more firmly identified in multiple mammalian species. Such observations provide the basis for considering the existence of reflexes arising in the kidney and affecting cardiovascular and renal mechanisms important in the regulation of arterial pressure, regional vascular resistance, and body sodium and water balance.

4 Physiological Functions of the Renal Nerves

4.1 Control of the Renal Circulation

The regulation of renal blood flow (Aukland 1976, 1980a,b) and the reflex influences of the arterial baroreceptors, cardiopulmonary mechanoreceptors, and chemoreceptors on the renal circulation (Kirchheim 1976; Linden 1975; Donald and Shepherd 1978, 1980; Thames 1978; Thoren 1979; Coleridge and Coleridge 1980) have been dealt with in several recent comprehensive reviews. The question of whether the kidney possesses sympathetic cholinergic vasodilator fibers (Stinson et al. 1969) has been reexamined (Zambraski et al. 1978). Using isolated carotid sinus perfusion techniques to increase carotid sinus pressure and inhibit efferent RSNA, renal blood flow increased by only 5% and renal vascular resistance decreased by only 4%; these small changes in renal blood flow and renal vascular resistance were unaffected by renal arterial administration of atropine (Fig. 4). The maximum renal vasodilator response to reduction of renal perfusion pressure below the autoregulatory range was not affected by renal arterial administration of atropine. The renal vasoconstrictor response to graded direct electrical renal nerve stimulation was abolished by renal adrenergic blockade with guanethidine and never replaced by a renal vasodilator response. These experiments indicate that there are no functional renal sympathetic cholinergic vasodilator fibers. These observations are in agreement with previous studies by Takeuehi et al. (1961, 1965, 1971), Brody (1962), Coneha and Norris (1968), Ueda et al. (1968), DiSalvo and Fell (1971), and Gomer and Zimmerman (1972). In addition, these studies provide physiological support and confirmation of Barajas and colleagues' sophisticated anatomical studies which demonstrate that the acetylcholinesterase- containing nerve terminals are adrenergic (Bara]as et al. 1974, 1975, 1976). 100 G.F. DiBona

N:22 Fig. 4. Effect of increasing carotid sinus RBF 240F%° F pressure (CSP) on renal perfusion pres- ml/min sure (RPP, held constant), renal blood 220E- flow (RBF) and renal vascular resistance (R VR) in the anesthetized dog. C, control; E, experimental; R, recovery; AP, arterial pressure. (Zambraski et al. 1978) RVR 0.506I mmHVml/mir 0.4

160

140 AP rnrnHg 120i CSP~

lOC RP P *~----,-~ T

However, activation of other reflex pathways has been demonstrated to result in a reduction in efferent RSNA or a renal vasodilatation or both. Increases in hepatic portal venous pressure (portal vein occlusion) produce decreases (Nii]ima 1976) or no change (Kostreva et al. 1980) in efferent RSNA and renal vasodilatation (Nii]ima 1976). Stimulation of left atrial cardiopulmonary receptors decreases efferent RSNA (Karim et al. 1972; Prosnitz and DiBona 1978) and results in modest renal vasodilatation (Mason and Ledsome 1974; Lloyd and Friedman 1977). Kahl, Flint, and Szidon (1974) noted that the magnitude of the renal vasodilatation was minimal when initial renal vasomotor tone was low, but was substantial when initial renal vasomotor tone was high due to spontaneous renal vasoconstriction. Using conditions of controlled carotid sinus pressure and measuring renal blood flow at a constant systemic pressure, Karim and Kappagoda (1980), in a preliminary report, showed that the renal vasodilator response to left atrial receptor stimulation was greatest (11%) when carotid sinus pressure was lowest, i.e., when the inhibitory effect of carotid sinus baroreceptors on efferent RSNA was minimal. However, there was no difference between the responses at medium and high carotid sinus pressure. This effect was abolished by either cutting or cooling the cervical vagi. As reviewed by Thames and Abboud (1979a, b), coronary artery occlusion is known to produce reflex decreases in efferent RSNA and renal vasodilatation mediated by left ventricular receptors with vagal afferents located mainly in the distribution of the circumflex coronary artery (Thames et al. 1978; Walter et al. 1978). Although Stinson et al. (1976) suggested that the renal vasodilatation was cholinergically mediated, atropine administration decreased basal renal blood flow, thus making The Functions of the Renal Nerves 101 these results difficult to interpret. Thoracic afferent nerve stimulation at low frequencies (3 Hz) produced an inhibition of efferent RSNA and a renal vasodilatation which was enhanced following vagotomy (Purtock et al. 1977). However, while it is likely that these reflex vasodilator responses are related to the simultaneous reflex decrease in efferent RSNA, studies to assess the possible role of renal sympathetic cholinergic vasodilator fibers have not generally been reported. Aukland has extensively reviewed the available methologies for measuring the regional distribution of blood flow within the kidney (Aukland 1980a, b). None of the currently available techniques is sufficiently free of methodological limitations to allow meaningful interpretation of results. In particular, because of unacceptable theological problems, it does not appear possible to estimate changes in renal cortical blood flow distribution from the deposition of microspheres. Several recent studies deal with the relative influence of neuroadrenergic stimuli on the glomerular afferent and efferent arterioles (Blantz 1980). Utilizing newer micropuncture techniques in rats with accessible surface glomeruli, it has been shown that norepinephrine administration (Myers et al. 1975) increases efferent but not afferent arteriolar resistance when renal perfusion pressure is constant. However, Andreucci et al. ( 1976a, b) concluded, using similar parenteral infusions of norepinephrine, that the afferent glomerular arteriole was the major site of action for catecholamines. Although a preferential effect of norepinephrine on the efferent arteriole agrees with the older observations on epinephrine by Richards and Plant (1922), subsequently supported by Smith et al. (1940), the work of Gomez (1951) demonstrated that constancy of glomerular filtration rate in the face of a reduction in renal blood flow required equal changes in afferent and efferent arteriolar resistance. Subsequently, Smith (1951) also acknowledged this. However, Click et al. (1979) have studied the vascular reactivity of afferent and efferent arterioles of glomeruli transplanted into the hamster cheek pouch. Application of norepinephrine produced greater reductions in the luminal diameter of afferent than efferent arterioles, whereas application of angiotensin II produced slightly greater reductions in the luminal diameter of efferent than afferent arterioles. Afferent arterioles were more responsive to norepinephrine than angiotensin II, while the reverse was true for efferent arterioles. Thus, these direct studies indicate that both afferent and efferent glomerular arterioles respond to norepinephrine with vasoconstriction and that the afferent arteriole is more reactive to norepinephrine than the efferent arteriole. In companion studies, Gilmore et al. (1980) have shown that the preafferent and afferent glomerular arterioles are capable of myogenic responses when subjected to increases or decreases in extravascular pressure; a decrease in extravascular pressure decreased and an increase in 102 G.F. DiBona

extravascular pressure increased the arteriolar luminal diameter. Angio- tensin II antagonist (saralasin) and prostaglandin synthesis inhibitor (indomethacin) did not affect these responses, whereas they were abolished by papaverine. Conversely, the efferent glomerular arterioles responded pas- sively to changes in extravascular pressure with changes in luminal diameter being inversely related to changes in extravascular pressure. In rat micropuncture studies, parenteral angiotensin II infusion increased both afferent and efferent arteriolar resistance when renal perfusion pressure was kept constant (Myers et al. 1975;Blantz et al. 1976). Concurrent administration of the angiotensin II receptor antagonist, saralasin, restored efferent but not afferent arteriolar resistance to normal (Steiner and Blantz 1979). During conditions where endogenous intrarenal angiotensin II is increased, increases in afferent and efferent arteriolar resistance are observed. In chronic sodium deprivation, saralasin administration decreases afferent but not efferent arteriolar resistance (Stei- ner et al. 1979). Activation of the tubuloglomerular feedback system increases both afferent and efferent arteriolar resistance (Tucker et al. 1978); both are decreased by saralasin administration (Tucker and Blantz 1978). These observations help explain the responses of renal blood flow and glomerular filtration rate to direct electrical renal nerve stimulation. During intensities which caused less than 15% reduction in renal blood flow, it was noted that glomerular filtration rate remained normal. How- ever, renal nerve stimulation after propranolol (Johns et al. 1976), angiotensin I converting enzyme inhibitor (Johns 1979), or angiotensin II antagonist (Johns 1980) administration was associated with a decrease in glomerular filtration rate despite an identical reduction in renal blood flow. It was suggested that angiotensin II liberated during renal nerve stimulation prevents glomerular filtration rate from decreasing by constricting the efferent arteriole to maintain glomerular hydrostatic pressure constant. The liberate norepinephrine would act preferentially on the afferent arteriole, while the resultant angiotensin II would act preferentially on the efferent arteriole; removal of the angiotensin II efferent arteriolar vasoconstrictor effect would not greatly affect renal blood flow, but, by decreasing glomerular hydrostatic pressure, would decrease glomerular filtration rate. Similar observations have been made in response to reductions in renal perfusion pressure in the dog (Hall et al. 1977a, b) and in the cat (Johns 1979). Dopamine-induced renal vasodilatation has been extensively studied and has been reviewed recently by Goldberg and colleagues (Goldberg et al. 1978; Goldberg 1979; GoMberg and Kohli 1979). Bell and Lang (1973) have produced physiological evidence for the existence of renal dopaminergic innervation which is capable of mediating renal vasodilatation. Electrical stimulation of the hypothalamus or midbrain resulted in The Functions of the Renal Nerves 103

renal vasodilator responses which were unaffected by guanethidine, atropine, or mepyramine but were abolished by haloperidol. The doses of haloperidol employed were shown to abolish the renal vasodilator responses to dopamine, but did not affect the femoral vasodilator responses to isoproterenol. These results indicate that the renal vasodilator responses to central stimulation were mediated by renal vascular innervation which released dopamine as a neurotransmitter. Dinerstein et al. (1979) have provided evidence for the existence of dopamine-containing neuronal elements in the canine kidney. Changes induced by hydrochloric acid in the excitation spectrum of catecholamine fluorophores associated with the innervation of the canine renal vasculature demonstrated that there are neuronal elements at the glomerular vascular poles which contain predominantly dopamine. In contrast, the catecholamine fluorescence in the periadventitial layer of the arcuate arteries is derived from norepinephrine. These observations agree with the studies of Bell et al. (1978) which, using indirect pharmacological evidence, indicated that dopamine-containing vasomotor nerves are present in the dog kidney. Although the presence of pulse-synchronous efferent RSNA has been demonstrated in conscious unanesthetized cats, rats, and dogs (vide supra), discussion continues as to its renal hemodynamic and physiological significance. Surgical or pharmacological renal denervation in conscious unanesthetized dogs (Berne 1952; Pomeranz et al. 1968; Sadowski et al. 1979a, b) or normotensive man (Hollenberg et al. 1971) does not increase renal blood flow or decrease renal vascular resistance. In addition, although high pressure arterial baroreceptors (Kezdi and Geller 1968) and low pressure left atrial cardiopulmonary mechanoreceptors (Karim et al. 1972; Prosnitz and DiBona 1978) are known to influence efferent RSNA, their influence on renal blood flow and renal vascular resistance in conscious unanesthetized animals is quite small (Vatner 1974; Kaczmarezyk et al. 1978; Gross et al. 1979). This discrepancy may reflect the fact that the neurophysiological recording and renal hemodynamic studies have not been performed under comparable conditions. Gross and Kirchheim (1980), using conscious dogs, showed that bilateral common carotid artery occlusion increased efferent RSNA by 62%, whereas renal blood flow was unaffected whether renal perfusion pressure was held constant or allowed to rise. Using auditory stimuli, they demonstrated that a gun shot decreased renal blood flow by 40%, whereas a lesser stimulus, hand clap or whist- ling, increased efferent RSNA by 502%. These results suggest that the difference in the renal vasoconstrictor responses elicited by carotid occlusion and auditory stimuli was caused by a quantitatively different neural output to the kidney, with the increase in efferent RSNA to the kidney during carotid occlusion being insufficient to produce renal vasoconstriction. 104 G.F. DiBona

However, it is abundantly clear that such increases in efferent RSNA can alter renin release and renal tubular sodium reabsorption. In agreement with these observations are further studies by Gross et al. (1979) on the effect of carotid occlusion on renal blood flow in the conscious dog subjected to nonhypotensive hemorrhage. Whether renal perfusion pressure was held constant or not, renal blood flow was within 5% of control during carotid occlusion during normovolemia and hypo- volemia (16% blood loss). Since the response was identical following aortic nerve section, these results indicate that the renal blood flow response was due to autoregulation without inhibitory influences through the aortic baroreceptors, since there was no renal blood flow reduction of neurogenic or humoral origin when renal perfusion pressure was held constant. These conscious unanesthetized dog studies differ from the results of Oberg and White (1970) in the anesthetized cat, and from those of Mancia and colleagues (1973, 1976) in the anesthetized dog. They found that withdrawal of inhibition exerted by cardiopulmonary receptors with vagal afferents produced modest effects in the presence of normally functioning arterial baroreceptors, but pronounced effects after elimina- tion of the inhibitory influences from the arterial baroreceptors. As discussed by Thoren (197.9), in the anesthetized animal interruption of cardiopulmonary vagal afferents will tend to increase the gain of the carotid baroreceptor reflex, whereas increased activity of the cardiopulmonary receptors following volume expansion will tend to decrease it. These observations, taken together with the inability of the cardiopulmonary receptors to affect cardiovascular hemodynamics when the arterial baroreceptors are maximally activated, suggested that these two groups of receptor afferents may converge on the same neuron pools within the vasomotor center. However, there seems to be clear evidence for the existence of a differentiated control of sympathetic outflow to various vascular beds in response to a reduction in baroreceptor afferent activity. For example, reduction in carotid sinus pressure in anesthetized dogs with aortic nerves sectioned decreased renal blood flow by approximately 20%, whereas muscle blood flow decreased by approximately 80% (Pelletier and Shepherd 1975a). However, when excitatory influences from chemoreceptor or somatic afferents are simultaneously activated, this differentiated response is abolished and withdrawal of baroreceptor inhibition also induces a maximal renal vasoconstriction (Pelletier and Shepherd 1975b). Folkow et al. (1961) suggested that the central neuron pools which control the sympathetic outflow to the renal resistance vessels have a low ex- citability and hence a weak spontaneous or tonic activity. Therefore, in the conscious animal, a reduction in baroreceptor afferent activity probably produces only small changes in the low tonic activity of the renal vasomotor neurons. In contrast, in the anesthetized operated animal it is The Functions of the Renal Nerves 105 likely that there is an enhanced level of tonic activity which becomes manifest when the renal vasomotor neurons are released from baroreceptor restraint. This hypothesis is supported by the fact that in those studies which reported a neurogenic renal vasoconstriction after carotid sinus hypotension an elevated resting renal vasoconstrictor tone was detected (Kendrick et al. 1972;Mancia et al. 1976;Pelletier and Shepherd 1975a). The cardiopulmonary receptors can also influence the renal vascular response to somatic afferent input. Thames and Abboud (1979b) examined the renal vasoconstrictor responses to afferent sciatic nerve stimulation in anesthetized dogs with sinoaortic denervation. During isovolemia, sciatic stimulation produced renal vasoconstriction; this response was attenuated by volume expansion and augmented by vagotomy. Similar responses were seen when the carotid sinuses were isolated and perfused at constant pressure. Thus, in the absence of the arterial baroreceptors or with intermediate levels of carotid baroreceptor activation, volume expansion with augmentation of discharge of cardiopulmonary receptors with vagal afferents markedly attenuated the renal vasoconstrictor responses to somatic afferent stimulation. The effects of various humoral substances on vascular neuroeffector mechanisms have been recently summarized (Bevan 1978; Westfall 1980). Evidence has accumulated which supports the existence of a presynaptic ~-adrenoceptor-mediated inhibitory mechanism regulating the release of neuronal norepinephrine from adrenergic nerves (Starke 1977, 1981 a, b; Westfall 1977; Rand et al. 1980). The postsynaptic ~-adrenoceptor has been designated a-1 and the presynaptic ~-adrenoceptor, ~-2 (Berthelsen and Pettinger 1977). In this regard, Robie (1980) has evaluated the functional significance of presynaptic ~-2 adrenoceptor modulation of renal sympathetic nerve function in the dog. Using ~-adrenoceptor agonists and antagonists and inhibitors of neuronal uptake, there was no evidence of a physiologically significant ~-adrenoceptor-mediated negative feedback mechanism on renal sympathetic nerve stimulation-induced renal vasoconstriction. On the other hand, acetylcholine produced inhibition of renal vasoconstrictor responses to renal sympathetic nerve stimulation that were dose and frequency dependent; the inhibition was blocked by atropine but unaffected by physostigmine. The effect of acetylcholine was not due to renal vasodilation per se since another renal vasodilator compound, sodium acetate, was ineffective (Robie 1979). Similar findings were observed with histamine (Robie 1981). The renal vasoconstrictor responses to renal sympathetic nerve stimulation are reduced by ureteral occlusion (Schramm and Carlson 1975) and by decreases in renal perfusion pressure (Carlson and Sehramm 1978). The inhibition was only partially reversed by blockade of prostaglandin synthesis in agreement 106 G.F. DiBona

with observations demonstrating increased renal prostaglandin production during ureteral occlusion (Olson et al. 1976) and reduction in renal perfusion pressure (McGiff et al. 1970). The remainder of the inhibition was ascribed to mechanical factors related to the presence of autoregulatory vasodilation. During dietary sodium deprivation in dogs, the renal release of norepinephrine, renin, and prostaglandin is increased as compared to values in dogs on a normal dietary sodium intake (Davila et al. 1978; Oliver et al. 1980b; Blasingham et al. 1980). Although dietary sodium deprivation decreased cardiac output and increased total peripheral vascular resistance, mean arterial pressure, renal blood flow, and renal vascular resistance were unchanged. Administration of the prostaglandin synthesis inhibitors indomethacin or meclofenamate to sodium-replete dogs decreased urinary prostaglandin excretion but did not affect mean arterial pressure, cardiac output, renal blood flow, renal vascular resistance, urinary water, sodium or potassium excretion, or plasma renin activity. When administered to sodium-deprived dogs, however, indomethacin or meclofenamate decreased urinary excretion and renal release of prostaglandin, renal blood flow, and urinary flow rate, and increased renal vascular resistance; mean arterial pressure, cardiac output, urinary sodium and potassium excretion, and plasma renin activity were unaffected. Thus, chronic sodium depletion enhances the activity of three major neurohumoral systems capable of directly influencing renal vascular resistance. The renal vasoconstrictor response to indomethacin or meclofenamate seen during chronic sodium depletion but not repletion indicates that renal blood flow is maintained during chronic sodium depletion by an effect of the prostaglandins which cause renal vasodilatation. Similar conclusions were reached by Zambraski and DiBona (1979), who showed that combined renal a-adrenoceptor and angiotensin II receptor blockade did not affect the renal vasoconstrictor response to indomethacin or meclofenamate in anesthetized surgically stressed dogs. Similar findings with both pharmacological (phenoxybenzamine) and surgical renal denervation have also been reported by Ehrhart et al. (1979). Taken together these results indicate that the renal vasoconstriction associated with systemic administration of prostaglandin synthesis inhibitor is not due to unopposed angiotensin II or a-adrenoceptor agonist vasoconstrictor action, but rather to the withdrawal of endogenous prostaglandin renal vasodilator activity. As recently summarized by Epstein and Litschitz (1980), there are several clinical disease states partly characterized by decreased effective blood volume with avid renal sodium retention (cirrhosis with ascites, nephrotic syndrome, chronic diuretic abuse, and congestive heart failure) wherein administration of prostaglandin synthesis inhibitors produces marked reductions in glomerular filtration rate The Functions of the Renal Nerves 107

(acute renal insufficiency) with enhanced renal sodium retention. In dogs with experimental cirrhossis and ascites produced by common bile duct ligation, Zambraski and Dunn (1980) reported that indomethacin administration produced marked renal vasoconstriction with decreased glomerular filtration rate. Taken together, these several observations suggest that heightened renal prostaglandin synthesis may be an important part of the renal adaptive mechanism in states of reduced effective blood volume. In- hibition of these prostaglandin functions may result in marked renal functional impairment with excessive renal sodium and water retention. In summary, a variety of reflex mechanisms operating singly or in concert are capable of producing significant renal circulatory changes which are mediated by efferent RSNA. Work in conscious unanesthetized animals has further defined the relationship between basal levels of efferent RSNA and the response of both efferent RSNA and renal blood flow to activation of some of these reflex mechanisms. In agreement with anatomical studies, there is no functional evidence to support the existence of sympathetic cholinergic vasodilator fibers in the mammalian kidney.

4.2 Control of Renal Tubular Solute and Water Transport

Investigation of renal solute and water excretion may be said to have begun with Claude Bernard (1859), who demonstrated an ipsilateral diuresis in the anesthetized dog following acute section of the greater splanchnic nerve. The diuresis was reversed by direct electrical stimulation of the peripheral cut end of the nerve. Research on the subject of the neural control of renal tubular transport processes has continued over the inter- vening years and investigators have generally employed one of two experimental approaches. If the renal nerves participate in the control of renal tubular electrolyte and water transport, then it was reasoned that increases or decreases in efferent renal nerve activity should produce reciprocal changes in renal electrolyte and water excretion. To decrease efferent renal nerve activity, the technique of renal denervation has been used; to increase efferent renal nerve activity, the technique of direct electrical stimulation of the renal nerves has been used. Less commonly, reflex interventions have been employed to decrease or increase renal nerve activity.

4.2.1 Renal Denervation

Since the initial observation of Bernard (1859), a large number of studies of denervation diuresis and natriuresis have been published. Two mechanisms have received support from the results of such studies. First, the increase in urinary sodium excretion has been ascribed to an increase in 108 G.F. DiBona glomerular filtration rate and filtered sodium load (e.g., Berne 1952). Second, the increase in urinary sodium excretion has been ascribed to a decrease in renal tubular sodium reabsorption (e.g., Bon]our et al. 1969; reviewed by Takacs et al. 1978). While the supportive evidence for each mechanism appeared equally distributed, newer investigations since the unequivocal demonstration that mammalian renal tubules receive adrenergic innervation (Barajas 1978) have provided growing support for a role of the renal nerves to directly influence renal tubular sodium and water reabsorption. Initially, Bencsath et al. (1972) in the rat, demonstrated by micropuncture that acute section of the left major splanchnic nerve resulted in decreased proximal tubular reabsorption of sodium and water without a change in single nephron glomerular filtration rate. The ipsilateral diuresis and natriuresis were not associated with changes in total kidney or single nephron glomerular filtration rate or the ratio of superficial to juxtamedullary single nephron glomerular filtration rate. Bello-Reuss et al. (1975, 1977) acutely denervated the kidney in both hydropenic and volume-expanded rats. They observed an ipsilateral diuresis and natriuresis in the absence of a change in total kidney or single nephron glomerular filtration rate or renal plasma flow. Absolute and fractional sodium and water reabsorption in the proximal tubule were decreased. There was no change in pressure as measured in several cortical microvascular structures, indicating that changes in peritubular Starling forces were not responsible for the observed changes in renal proximal tubular reabsorption. Absolute sodium and water reabsorption increased after denervation in the loop of Henle, distal convoluted tubule, and collecting duct. During hydropenia, the contralateral innervated kidney responded to acute denervation of the other kidney with no change in urinary flow rate or sodium excretin. However, during volume expansion, the contralateral innervated kidney responded to acute denervation of the other kidney with a decrease in urinary flow rate and sodium excretion. The localization of the effect to the proximal tubule by micropuncture confirmed earlier suggestions based on indirect measurements by Kaplan and Rapaport (1951), Blake (1962) andBencsath et al. (1971). Wilson et al. (1979b)have confirmed that both acute and chronic renal denervation in anesthetized non-volume-expanded rats produces an ipsilateral diuresis, natriuresis, and kaliuresis without a change in glomerular filtration rate or renal plasma flow; no changes in function of the contralateral kidney were observed. Using renal clearance studies in anesthetized, hypophysectomized dogs undergoing a water diuresis, Nornura et al. (1972, 1976, 1977) showed that renal denervation increased ipsilateral urinary flow rate and sodium excretion without changing glomerular filtration rate or renal plasma flow. Fractional sodium delivery to the distal The Functions of the Renal Nerves 109 nephron and fractional free water clearance were significantly increased in the denervated kidney, suggesting the proximal tubule as a site of the decreased tubular sodium and water reabsorption. The renal denervation effect of diuresis and natriuresis is not a transient one that is observed only immediately after denervation, since similar results have been observed in chronically denervated kidneys of rats (Bencsath et al. 1979), and dogs (Takacs et al. 1978). Kurkus et al. (1980) have shown that, in dehydrated conscious dogs, urinary osmolality, medullary total solute, and sodium content (per kg wet tissue) were significantly lower in the denervated kidney as compared to the innervated kidney. This may be explained by the fact that the weight of the denervated kidneys was significantly higher than the weight of the innervated kidneys. It was postulated that renal denervation resulted in an increase in renal tissue water content. Pharmacological renal denervation has also been employed. In anesthetized dogs, administration of guanethidine into the renal artery with the simultaneous intravenous administration of phenoxybenzamine to anta- gonize the systemic vasoconstrictor effects of liberated norephinephrine produced an ipsilateral increase in the urinary excretion of water, sodium, potassium, chloride, and calcium, while renal perfusion pressure, glomerular filtration rate, and renal blood flow remained unchanged (Williams et al. 1971). Renal a-adrenoceptor blockade with phenoxybenzamine increased urinary flow rate and free water excretion without changing urinary sodium excretion or glomerular filtration rate in anesthetized, hypophysectomized, steroid-replaced dogs undergoing a water diuresis. It was suggested that a-adrenoceptor blockade decreased proximal tubular sodium reabsorption (Gill and Casper 1971). However, in anesthetized hydropenic dogs, renal arterial administration of phenoxybenzamine increased urinary sodium excretion without changing renal blood flow or glomerular filtration rate; by micropuncture, proximal tubular sodium and water reabsorption were unaltered, suggesting that the natriuresis derived from more distal nephron segments (Strandhoy et al. 1974). Renal arterial administration of phenoxybenzamine does not produce a natriuresis in conscious unanesthetized dogs (Barger et al. 1959a, b). Renal/~-adrenoceptor blockade generally produces an antinatriuretic response which has been attributed to renal hemodynamic alterations (Epstein and Braunwald 1966; Nies et al. 1971; Nomura et al. 1978;Prosnitz andDiBona 1980), a direct renal tubular effect (Cacciaguida et al. 1969), or an involvement of the renal sympathetic nervous system (Waugh 1970; Mroczek et al. 1970). However, a natriuretic response has also been described (Lees 1968; Klein et al. 1971 ; Carrara and Baines 1976). Recently, evidence has been presented that there is a similar effect of renal a-adrenoceptor blockade on renal tubular sodium and water reabsorption in an amphibian, the bullfrog (Gallardo et al. 1980). Using a 110 G.F. DiBona doubly perfused in situ kidney preparation, phenoxybenzamine, when added to the portal venous perfusate which is solely distributed to the tubules, produced a natriuresis and diuresis which was independent of any changes in glomerular filtration rate or renal perfusion outflow. Neural elements in close proximity to renal tubules were observed with both light and electron microscopic techniques (Pang et al. 1982). It has long been argued that denervation diuresis and natriuresis is an artifact produced by the stress of anesthesia and surgery in experimental animals, which artificially increases sympathetic tone to the kidneys resulting in an effect in excess of what can be seen in the unanesthetized conscious state (Smith 1951). Lifschitz (1978) subjected conscious dogs with one kidney denervated and the other kidney intact to sequential random- ordered hemorrhage (2% body weight) and volume expansion (isotonic Ringer solution, 5% body weight). In terms of sodium handling, the denervated kidney responded as well as the innervated kidney during both hemorrhage and volume expansion. Sadowski et al. (1979a, b, 1980) studied conscious dogs with one kidney denervated and the other kidney intact. During hydropenia, the denervated to innervated kidney ratio for urinary sodium excretion factored for glomerular filtration rate significantly exceeded 1.0, thus indicating a defect in renal tubular sodium reabsorption in the denervated kidneys. These studies confirm the older observations in conscious unanesthetized dogs by Benchetrit et al. (1966). Schnei- der et al. (1978) studied the effect of chronic bilateral renal denervation on the ability of the conscious dog to adjust urinary sodium excretion to changes in dietary sodium intake. In the sham renal denervated dogs, urinary sodium excretion was the same during experimental and control phases whether on a dietary sodium intake of 100 or 3 mEq per day. In the renal denervated dogs there was no difference on the 100 mEq per day sodium diet, but on the 3 mEq per day sodium diet urinary sodium excretion was twofold higher after than before renal denervation. Gordon et al. (1979) studied the ability of conscious rabbits with chronic bilateral renal denervation or systemic sympathetic blockade produced by reserpine or guanethidine treatment to adapt to dietary sodium restriction. In response to reduction in dietary sodium intake, neither group was able to reduce urinary sodium excretion sufficiently to avoid negative external sodium balance. This defect was reversible in the guanethidine- or reserpine-treated group. Rogenes and Gottschalk (1980) have presented data from studies in conscious euvolemic and volume- expanded rats showing that the chronically denervated kidney has a higher urinary flow rate and sodium excretion than the intact kidney. These conscious animal studies are in good agreement with several observations in man. Gill and Bartter (1966) demonstrated that normal subjects in whom autonomic insufficiency had been produced by guanethidine administra- The Functions of the Renal Nerves 111

tion were unable to lower urinary sodium excretion sufficiently to avoid negative external sodium balance in response to a reduction in dietary sodium intake, despite decreases in glomerular filtration rate. Wilcox and colleagues (1977) demonstrated similar findings in patients with idiopathic autonomic insufficiency. Obese human subjects placed on a hypocaloric protein diet show a decrease in sympathetic nervous system activity, with a reduction in basal plasma norepinephrine concentration and a failure of plasma norepinephrine concentration to increase in response to upright posture. The subjects showed a significant net sodium loss (-382 mEq per 21days or -18 mEq/day on a sodium intake of 54 mEq/day) and a pronounced orthostatic decrease in systolic blood pressure (-28 mmHg) with symptoms of orthostatic hypotension (DeHaven et al. 1980). Thus, this dietary regime produces signs and symptoms of idiopathic autonomic insufficiency with inability of the kidney to conserve sodium in response to a modest reduction in dietary sodium intake. Although Blaufox et al. (1969a) demonstrated that the transplanted human kidney, could normally conserve sodium on a dietary sodium intake of 10 mEq per day, these studies were conducted 46-922 days after surgery. Since Gazdar (1969) and Gazdar and Dammin (1970) have demonstrated neural regeneration in

NORMAL LOW SODIUM SODIUM 1.0

.6 INNERVATED

E .2

N=8 ?

E ~ -.4 DENERVATED

-.8 Fig. 5. Effect of renal denervation on renal adaptation to dietary -1.0 i 'o ' sodium restriction in conscious rats. 0 5 1 15 (DiBona and Sawin 1981) Days 112 G.F. DiBona

human renal transplants as early as 38 days after surgery, it is clear that the results of Blaufox et al. (1969a) could be explained by undetected regeneration of renal nerves. Similar studies performed in the early post- transplant period will be required to accurately assess the contribution of intact renal innervation to normal renal physiological responses in man (Blaufox et al. 1969b; Norvell 1970). Recent studies in our laboratories (DiBona and Sawin 1981) demonstrate that renal denervation renders the conscious rat unable to maintain positive external sodium balance when dietary sodium intake is restricted (Fig. 5). Thus, the evidence from studies in anesthetized and conscious unanesthetized animals and human subjects indicates that when the kidney is deprived of its innervation, renal tubular sodium and water reabsorption are directly decreased. Of even more importance is the fact that intact renal innervation appears to be essential for the kidney to express its full ability to maximally reabsorb sodium in response to a reduction in dietary sodium intake. Therefore, the renal nerves are an important component of the efferent mechanism of the body's defense against sodium and, thus, extracellular fluid volume depletion. The direct influence of renal innervation on renal tubular sodium reabsorption has been more easily and clearly demonstrable in pathological states characterized by enhanced renal tubular sodium reabospriton. Whelan et al. (1952) noted that dogs with a transplanted kidney in the neck did not develop ascites as rapidly after thoracic inferior vena cava constriction (TIVC) as dogs with an abdominal kidney and suggested that this difference might be due to the transplantation of the kidney. Brod et al. (1954) administered the a-adrenoceptor antagonist, dibenamine, intravenously to patients with congestive heart failure. He observed an increase in fractional sodium excretion without a significant change in renal blood flow or glomerular filtration rate; cardiac output increased and mean arterial pressure decreased slightly. Barger et al. (1959a, b) demonstrated that renal arterial administration of phenoxybenzamine or hexamethonium produced an ipsilateral diuresis and natriuresis, without a change in renal plasma flow or glomerular filtration rate, in conscious dogs with experimental congestive heart failure due to chronic tricuspid insufficiency. Gill et al. (1967) showed that systemic autonomic blockade with pentolinium increased urinary sodium excretion in dogs with chronic TIVC constriction, suggesting the presence of an increased level of sympathetic activity. Schrier et al. (1971) observed that the antinatriuretic effect of acute TIVC constriction was abolished by systemic autonomic blockade with hexamethonium or systemic a-adrenoceptor blockade with phenocybenzamine, but not by surgical renal denervation. However, Azer et al. (1972) found that surgical renal denervation partially restored the natriuretic response to intravenous isotonic saline loading in dogs with acute TIVC constriction. The Functions of the Renal Nerves 113

Slick et al. (1974) showed that either surgical or pharmacological renal denervation restored the natriuretic response to intravenous isotonic saline loading toward normal in dogs with acute TIVC constriction. This response was accompanied by a decrease in proximal tubular fractional and absolute water and sodium reabsorption in the absence of changes in systemic or intrarenal hemodynamics or changes in the intrarenal distribution of blood flow or filtrate. Thus, in experimental models of congestive heart failure, maneuvers which interrupt efferent RSNA elicit increases in urinary flow rate and sodium excretion which are attributable to decreases in renal tubular reabsorption with localization at least to the proximal tubule. Chronic ligation of the common bile duct leads to progressive development of ascites with a blunted natriuretic response to extracellular volume expansion (Better and Massry 1972). Both surgical and pharmacological (phenoxybenzamine) renal denervation produced slight but significant ipsilateral increases in urinary sodium excretion which were similar in the normal and chronic bile duct ligated dogs. However, neither intervention restored the normal natriuretic response to extracellular volume expansion (Chaimovitz et al. 1974). However, oral administration of propranolol restored the natriuretic response to extracellular volume expansion half- way to normal; this was attributed to an extrarenal effect of ~-adrenoceptor blockade (Winaver et al. 1978). The role of the renal nerves in determining the renal function following relief of ureteral obstruction has been studied by Wilson (1980). The renal nerves play a role in the decreased glomerular filtration rate, renal plasma flow, and altered sodium and water excretion which occur after relief of 24-h unilateral ureteral obstruction; chronic renal denervation was not protective against these functional changes (Wilson et al. 1979a). Renal denervation does not prevent the increased renal tubular sodium reabsorption that occurs with a mild increase in ureteral pressure due to partial ureteral obstruction (Wilson et al. 1979a). There is a significant increase in glomerular filtration rate, renal plasma flow, urinary flow rate, and sodium excretion with acute renal denervation after relief of unilateral ureteral obstruction, but no such response is seen after relief of bilateral ureteral obstruction. This may relate to the observation that renal tissue catecholamine concentrations, while normal in the unilateral ureteral obstruction kidney, are markedly decreased (but not to the postrenal denervation range) in the bilateral ureteral obstruction kidneys (Wilson and Honrath 1981). The extensive work of Takacs, Bencsath, Szalay, and colleagues has characterized the effect of renal denervation (major splanchnic nerve section) on several other tubular ion transport processes. In a series of dog studies it was demonstrated that renal denervation increased the excretion 1 14 G.F. DiBona and lowered the maximum tubular transport of phosphate (Szalay et al. 1977a), para-aminohippurate (Szalay et al. 1977b), glucose (Szalay et al. 1977c), and uric acid (Szalay et al. 1977e). In all studies, glomerular filtration rate was unchanged and urinary flow rate and sodium excretion were uniformly increased. It was suggested that efferent RSNA might generally regulate renal proximal tubular transport processes (Szalay et al. 1977d). The effect of renal denervation on renal tubular phosphate handling in the rat has been further studied. Szenasi et al. (1981) reported that both acute and chronic (21 dogs) renal denervation increased urinary phosphate excretion and decreased the maximum tubular transport of phosphate; identical observations were made in thyroparathyroidectomized animals, excluding a role for parathyroid hormone. Szalay et al. (1980) reported that volume-expanded rats with chronic renal denervation have increased urinary excretion of water, sodium, and phosphate as compared with volume-expanded sham-denervated control rats. In both early and late proximal tubular segments of the denervated kidneys, phosphate but not sodium and water reabsorption was inhibited. Thus, the observed diuresis and natriuresis were thought to derive from inhibition of water and sodium reabsorption beyond the proximal tubule or in deep nephrons. These observations suggest that the influence of the renal nerves on proximal tubular sodium transport is different from that on phosphate transport, and that other compensatory mechanisms restore proximal tubular sodium transport toward normal in the chronically denervated kidney. The role of the renal innveration in the renal excretory response to intravascular volume expansion has been discussed recently by Knox et al. (1980). They summarized the available evidence as indicating that intravascular volume expansion stimulates volume receptors, producing a decrease in efferent RSNA. The decrease in efferent RSNA directly decreases renal tubular sodium reabsorption in addition to producing changes in intrarenal hemodynamics which favor a decrease in renal tubular sodium reabsorption. This interpretation is supported by the recent studies of Sadowski et al. (1979a, b, 1980) who showed that the innervated kidney responded to isotonic saline volume expansion with a greater natriuretic response than the denervated kidney in both the unanesthetized and anesthetized states. Thus, the overall response of the innervated kidney to volume expansion includes a component relative to inhibition of efferent RSNA; such a component is lacking in the response of the denervated kidney. This disparity between the response of the innervated and the denervated kidney to volume expansion would be expected to be greater during anesthesia with the attendant increase in efferent RSNA. This was the case in that during the conscious state the increase in fractional sodium excretion was 1.7-6.4 fold (innervated) and 1.5-3.9 fold (denervated), and that during the anesthetized state it was 4.1-9.6 fold (innervated) The Functions of the Renal Nerves 115

and 2.7-3.2 fold (denervated). Similar findings were observed in the rat by Spencer and Yarger (1977). In examining the effect of renal denervation on renal function, two interrelated questions invariably arise. The first is the reliability of the renal denervation technique used, and the second is the potential adverse effects of the renal denervation technique on overall renal function. With regard to the first question, renal denervation requires physiological verification. In general, as discussed previously (DiBona 1977), a marked diminution in renal tissue norepinephrine concentration has been offered as evidence of complete renal denervation. However, this often requires 2-3 days to occur and, therefore, this method cannot be used to immediately verify the completeness of acute renal denervation at the time it is performed. In addition, the sensitivity of the methods used to measure renal tissue norepinephrine concentration is such that it is usually only possible to say that there has been approximately 90% reduction in renal tissue norepinephrine concentration. It is not fully understood what level of renal tissue norepinephrine concentration (biochemistry) is required to achieve full responses to increases in efferent renal sympathetic nerve activity (physiology). However, the recent studies of Kline and Mercer (1980a) in the rat indicate that 24-32 days following renal denervation, at a time when renal tissue norepinephrine concentration was 29% of the control level, renal vascular responses to renal nerve stimulation had returned to 40% of the control values. At 52-53 days following renal denervation, renal vascular responses to renal nerve stimulation had returned to 100% of control values, but hypersensitivity to norepinephrine was still present. In subsequent studies, Kline et al. (1980a) showed that, following renal denervation, renal tissue norepinephrine concentration had returned to 13%, 25%, 33%, and 35% of control values at 2, 4, 6, and 8 weeks. Thus, in studies in conscious animals with denervated kidneys even minor increases in circulating norepinephrine occurring in response to stresses such as mild to modest hemorrhage (Lifschitz 1978) could have significant physiological renal effects. Moss and Harrington ( 1981 ) showed that 1 week following renal denervation, renal tissue norepinephrine concentration was 10% of normal and basal urinary sodium excretion was increased by 157% above the control value. Basal urinary sodium excretion returned to normal within 2 weeks, while renal tissue norepinpehrine concentration showed a linearincrease to 50% of the normal value by 6 weeks. It seems that functional responses to renal nerve activation return more rapidly toward control levels than does the renal tissue norepinephrine concentration. In physiological studies, one is interested in knowing whether the functional effects of activation of the renal nerves have been abolished by the renal denervation procedure. As recently described (DiBona 1977;DiBona andRios 1980), renal denervation may be considered 116 G.F. DiBona

-50 Fig. 6. Effect of acute renal denerva- o--Olntact 1" T tion on the renal vasoconstrictor re- o---o Re2al DNX .L~ -40 sponse to direct electrical stimulation at 10 V and 0.5 ms duration of suprarenal lumbar sympathetic chain -30 or proximal renal nerve bundle. %A (DiBona and Rios 1980) RBF -20

-10 .... ~ ...... {_-t 0 2 4 8 10 Hz

complete when the renal vasoconstrictor response to direct electrical stimulation of the suprarenal lumbar sympathetic chain or the proximal renal nerve bundle is abolished (Fig. 6). An alternative approach is to demonstrate the abolition of the reflex renal vasoconstrictor response to bilateral carotid artery occlusion after bilateral cervical vagotomy (Kopp et al. 1980a). With regard to the second question, surgical renal denervation in its simplest form or in more complex forms involving autotransplantation (Bricker et al. 1958), or section and resuture of the renal artery, vein, and ureter (Quinby 1916) often adversely affects overall renal function (Katz and Shear 1975). Pharmacological renal denervation, while less traumatic, may be less complete than surgical renal denervation (Katz and Shear 1975). Thus, the interpretation of the results of studies employing renal denervation to assess the neural control of renal function has, to a certain extent, been hampered by the failure to consider these two important questions.

4.2.2 Direct Electrical Renal Nerve Stimulation Previous studies concerning the effects of direct electrical renal nerve stimulation on renal function were predominantly focused on changes in renal hemodynamics and utilized high levels of stimulation which produced marked decreases in glomerular filtration rate and renal blood flow (Houck 1951; Block et al. 1952a, b). Subsequently, investigators interested in the effects of direct electrical renal nerve stimulation on renal tubular sodium reabsorption used more modest levels of stimulation which, while not affecting glomerular filtration rate, still reduced renal blood flow (Johns et al. 1976). As discussed elsewhere (Schrier 1974;DiBona 1977), "the results do not differentiate between a direct effect on active sodium trans- The Functions of the Renal Nerves 117

port and an indirect effect mediated by some alteration in intrarenal hemodynamics." Our own observations in this field proceeded from the work of Barger et al. (Barger et al. 1959a, b), who demonstrated a role for efferent RSNA in the renal sodium retention observed in the conscious dog with experimental congestive heart failure. Unilateral renal arterial infusion of phenoxybenzamine produced an ipsilateral natriuresis and diuresis in the absence of changes in glomerular filtration rate or renal plasma flow. Using another experimental model of congestive heart failure in the dog, acute thoracic inferior vena cava constriction (Azer et al. 1972; Slick et al. 1975), it was demonstrated that either surgical or pharmacological renal denervation partially restored the natriuretic response to isotonic saline volume expansion without changes in renal hemodynamics. The reversal of the antinatriuresis was accomplished by an inhibition of proximal tubular sodium reabsorption, i.e., a restoration of the expected renal response to isotonic saline volume expansion. These studies strongly indicated that there existed a level of efferent renal sympathetic nerve activity which could directly affect renal tubular sodium and water reabsorption in the absence of changes in glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow. The study of La Grange et al. (1973) provided some initial evidence that such a level of efferent RSNA did, in fact, exist. Using direct electrical renal nerve stimulation (10-15 V, 0.5 ms, 0.33-1.0 Hz) in anesthetized dogs, they demonstrated a 13%-26% decrease in urinary sodium excretion, while glomerular filtration rate and renal blood flow were unchanged. Although these observations were consistent with a direct effect of the renal nerves on renal tubular sodium reabsorption, the authors considered this possibility unlikely since, at that time, definitive evidence of renal tubular innervation was lacking. Additionally, as a methodological limitation, glomerular filtrationrate was determined by a urineless technique based on the Fick principle. To further pursue this hypothesis, studies (Slick et al. 1975) were conducted in anesthetized dogs prepared for bilateral renal clearance and hemodynamic measurements. The distal portion of the transected renal nerve bundle was electrically stimulated using an intensity that was just below the threshold for a reduction in renal blood flow. This level of renal nerve stimulation produced an ipsilateral reversible decrease in urinary sodium excretion unaccompanied by changes in mean arterial or renal perfusion pressure, glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow (Fig. 7). This antinatriuretic response was abolished by renal a-adrenoceptor blockade with phenoxybenzamine (Zambraski et al. 1976a) (Fig. 8) or renal adrenergic blockade with guanethidine (Slick et al. 1975); it was unaffected by renal blockade to 1 18 G.F. DiBona

250 Fig. 7. Effect of low level renal nerve I I T stimulation (0.5-2.0 Hz) on urinary 200 sodium excretion (UNa V) in anesthe- UNa V tized dogs. Cin, inulin clearance; TRBF, total renal blood flow; CpAH, Eq/min 150 P< ,001 para-aminohippurate clearance; C, control, S, stimulation; R, recovery. LEFT KIDNEY o--- N=I7 (Slick et al. 1975) R/GHT KIDNEY •

CIN 2 i ..... ml/min 25

200

TRBF o 150 CpAH •

ml/min I O0 "6- T T

0 I I I C S R angiotensin II (Zambraski and DiBona 1976) or by prostaglandin synthesis inhibition (DiBona et al. 1977). Thus, these studies demonstrated that low level direct electrical renal nerve stimulation directly increases renal tubular sodium reabsorption via activation of renal tubular a-adrenoceptors. The response is not mediated by either angiotensin II or prostaglandins which are known to be released in response to renal nerve stimulation (Taher et al. 1976; Zambraski and DiBona 1976;Dunham and Zirnmerman 1970; Davis and Horton 1972;Johns et al. 1977). Bello-Reuss et al. (1976), using a similar direct electrical splanchnic nerve stimulation protocol in anesthetized saline-loaded rats, found a 25% decrease in ipsilateral urinary flow rate and sodium excretion without a change in single nephron or whole kidney glomerular filtration rate or renal plasma flow. Micropuncture demonstrated an increased proximal tubular fractional and absolute sodium and water reabsorption (Fig. 9). Analysis of renal nerve fiber conduction velocities suggested that the responses were mediated by the stimulation of slowly conducting unmyelinated fibers. Direct electrical renal nerve stimulation at higher intensities (5 V, 1 ms, 2 and 5 Hz) reduced single nephron glomerular filtration rate and glomerular plasma flow; although fractional water reabsorption to the distal tubule increased, absolute water reabsorption decreased in The Functions of the Renal Nerves 119

LEFT RENAL ARTERY I INFUSION 0.9% NoCI -~ 4--~ PHENOXYBENZAMiNE 5OO

400

300 LEFT KIDNEY UNoV pEq/min

2O(]

~00

i i i i i i C S R C S R 236.9 186.4 234.7 232.7 233.5 231.3 *-47.2 -+43.8 t469 --46,2 +464 -+46.2

Fig. 8. Effect of renal a-adrenoceptor blockade with phenoxybenzamine on antinatriuretic response to low level renal nerve stimulation (0.5-2.0 Hz) in anesthetized dogs. UNaV , urinary sodium excretion; C, control; S, stimulation; R, recovery. Numerical data are mean -+ SE. (Zambraski et al. 1976)

parallel with single nephron glomerular filtration rate (Hermansson et al. 1981). The effect of renal adrenergic stimulation with pharmacological agents on renal sodium and water handling has also been examined. Barger et al. (1959a, b) infused norepinephrine into the renal artery of conscious unanesthetized dogs and observed an antinatriuresis that was independent of changes in glomerular filtration rate or renal plasma flow; superimposi- tion of phenoxybenzamine reversed the antinatriuresis. Pearson and Williams (1968) suggested that renal arterial administration of norepinephrine increased and isoproterenol decreased renal tubular sodium reabsorption, unrelated to the variable changes observed in renal blood flow and glomerular filtration rate. In anesthetized, hypophysectomized, steroid- replaced dogs, renal arterial administration of norepinephrine in the presence of renal ~-adrenoceptor blockade decreased urinary flow rate and free water excretion without changing urinary sodium excretion or renal hemodynamics. From these indirect clearance studies it was suggested that a-adrenoceptor stimulation increased proximal tubular sodium re- 120 G.F. DiBona

GFR o.,0.6 E Fig. 9. Effect of low level splanchnic nerve ml/min/lOOg 0.5 stimulation (1.0 Hz) on renal function in anesthetized rats. GFR, glomerular filtration RPF 2"00 f rate; RPF, renal plasma flow; UNa V, urinary ml/min/lOOg 1.50L sodium excretion; SNGFR, single nephron glomerular filtration rate; percentagesrepresent UNaV 10 f cortical proximal tubular fractional water re- /.~Eq/min absorption. C1, control; $1, stimulation; C2, 5 recovery. (Bello-Reusset al. 1976)

SNGFR 50~ nl/min 40 : :--5 25

ABSOLUTE 20 WATER REABSORPTION nl/min 15

57±4% 47±4% 52±6% 10 I I I CI St C2 absorption (Gill and Casper 1972). In similarly designed experiments, renal arterial administration of isoproterenol in the presence of renal ~- adrenoceptor blockade increased urinary flow rate and free water excretion without changing urinary sodium excretion or renal hemodynamics. It was suggested that ~-adrenoceptor stimulation decreased proximal tubular sodium reabsorption (Gill and Casper 1971). However, direct renal micropuncture studies in anesthetized hydropenic dogs using comparable experimental protocols to those of Gill and Casper (1971,1972), failed to reveal any effect of either ~-adrenoceptor stimulation (Blendis et al. 1972) or/3-adrenoceptor stimulation (Blendis et al. 1972; Stein et al. 1972) on renal proximal tubular sodium and water reabsorption. Cant and Vander (1973) infused norepinephrine into the renal artery of anesthetized dogs at a dose which reduced renal blood flow by less than 10%; urinary sodium excretion fell by 36% whereas glomerular filtration rate was unchanged. Johnson and Barger (1981) used graded infusions of physiological doses of norepinephrine or epinephrine intravenously or directly into the renal artery of conscious dogs. Norepinephrine, intravenous or intrarenal, produced only modest decreases in urinary sodium excretion even at high renal arterial plasma norepinephrine concentrations Intrarenal epinephrine did not affect urinary sodium excretion, whereas intravenous epinephrine produced a marked decrease in urinary sodium excretion even at renal arterial plasma epinephrine concentrations in the lower physiological range. It was concluded that this effect is not mediated by a direct intrarenal action of epinephrine, but may be secondary to in- The Functions of the Renal Nerves 121 creases in efferent RSNA or circulating angiotensin II concentration. It is known that intravenous epinephrine infusions increase plasma renin activity, wheras infusions directly into the renal artery do not (Johnson et al. 1979b). Furthermore, angiotensin II can decrease urinary sodium excretion without alteraing glomerular filtration rate or renal blood flow (Johnson and Malvin 1977). However, the direct renal tubular antinatriuretic response to increases in efferent RSNA is independent of angiotensin II (Zambraski and DiBona 1976).

4.2.3 Reflex Alterations in Efferent Renal Sympathetic Nerve Activity Gill and Casper (1969) observed an antinatriuresis in experiments in which the renal nerves of a hemorrhaged animal were left intact but the blood perfusing the animal's kidney was derived from another normal animal. Although there was a significant decrease in renal blood flow and an increase in filtration fraction which complicated the interpretation, this study suggested that a reflex increase in neural stimuli to the kidney that was not sufficient to decrease glomerular filtration rate could increase renal tubular sodium reabsorption. To increase efferent RSNA more

2OO Left Kidney (16/9) 180

160 UNAV ~Eqlmin 140

120

100

C IN 40 r ml/min 35 [ j. t. 30

RBF 2oo f ._r---- i ! Fig. 10. Effect of decreased caro- ml/min tid sinus pressure (CSP) on renal 150 function in anesthetized dogs. zoo UNa V, urinary sodium excretion; Cin, inulin clearance; RBF, renal blood flow; MAP, mean arterial AP mo pressure; RPP, renal perfusion r,mH~ CSP pressure; C, control; E experi- ~Oo mental; R, recovery. (Zambraski et al. 1976) 1 I i C E R 122 G.F. DiBona

Phenoxybenzamine N = 6 Fig. 11. Effect of left renal a-adreno- I00 e-~Left o---Right ceptor blockade on the renal functional response to decreased carotid 75 sinus pressure in anesthetized dogs. See Fig. 10 for abbreviations. (Zam- UNAV 50 braski et al. 1976) uEq/min

:55 ClN rnl/min 25

CPAH 90 ml/min

AP 150 mm Hg

100 I I 1 C E R physiologically, studies (Zambraski et al. 1967b) were performed using isolated carotid sinus perfusion to increase efferent RSNA via the carotid baroreceptor reflex. Reduction of carotid sinus pressure led to a reflex increase in efferent RSNA which produced a decrease in urinary sodium excretion without changes in renal perfusion pressure, glomerular filtration rate, or renal blood flow (Fig. 10). This antinatriuretic response was blocked by phenoxybenzamine (Fig. 11) and guanethidine. In response to bilateral common carotid artery occlusion in anesthetized dogs, the kidney with renal perfusion pressure held constant showed a decrease in urinary flow rate and sodium excretion, whereas the kidney with increased renal perfusion pressure showed a pressure diuresis and natriuresis; glomerular filtration rate and renal blood flow were constant in both kidneys (Barger et al. 1959b; Prosnitz et al. 1977). The antidiuresis and antinatriuresis were blocked by intrarenal phenoxybenzamine (Barger et al. 1959b). Similarly, de Chatel (1978) showed that the pressure diuretic and natriuretic response to carotid occlusion was greater in the denervated than the innervated kidney. However, in conscious unanesthetized dogs, Gross et al. (1981) observed that glomerular filtration rate, renal blood flow, urinary flow rate, and sodium excretion were unchanged when renal perfusion pressure was held constant during bilateral carotid occlusion• Al- though efferent RSNA increased by 58% after bilateral carotid occlusion, The Functions of the Renal Nerves 123 the lack of an effect on renal blood flow and tubular sodium reabsorption may relate to the low resting efferent RSNA in the conscious dog, since higher degrees of activation of efferent RSNA (auditory or emotional stimuli, +500%) caused severe renal vasoconstriction. In companion studies (DiBona and Johns 1980; DiBona et al. 1981), carotid baroreceptor reflex activation of efferent RSNA by 60 ° head-up tilting produced a decrease in urinary sodium excretion without changes in renal perfusion pressure, glomerular filtration rate, or renal blood flow. This antinatriuretic response was abolished by surgical or pharmacological (phentolamine) renal denervation and by bilateral carotid sinus nerve section (Fig. 12). Neither the antinatriuretic nor the renin-release response were affected by bilateral cervical vagotomy (DiBona et al. 1981). The role of the arterial chemoreceptors in the renal functional response to acute hypoxic hypoxia has recently been reviewed (Honig 1979). Acute hypoxic hypoxia stimulates carotid chemocreceptors, resulting in increased efferent RSNA with renal vasoconstriction but decreased renal tubular sodium and water reabsorption; renal denervation reverses the former but not the latter (Honig et al. 1979; Honig and Schmidt 1980). Hypercapnic acidosis has been shown to produce a decrease in urinary sodium excretion with unchanged glomerular filtration rate and renal blood flow; the antinatriuresis was significantly reversed by renal denervation (Anderson et al. 1980).

170

rr 150 ~

.= E

E • •

'°30 f ~ q= (5 o Intact, N=9 • Renal DNX, N=8 110: A Renal a Block, N=5 D CS DNX,N=8 Fig. 12. Effect of 60 ° head- 100 up tilt on renal function in z anesthetized dogs. RBF, renal o blood flow; GFR, glomerular 9O filtration rate; UNaV, urinary >

sodium excretion; C, control; = 8O Renal DNX, renal denerva- ton; Renal a Block, phentolamine; CS DNX, carotid sinus 7O denervation. and I I (DiBona C 60°Tilt Johns 1980) 10 min. 124 G.F. DiBona

Thus, both direct and reflex increases in efferent renal sympathetic nerve activity directly increase renal tubular sodium and water reabsorption via activation of renal tubular a-adrenoceptors. Since a physiological control system usually operates in a bidirectional manner, it was of interest to determine whether decreases in efferent RSNA would result in decreases in renal tubular sodium and water reabsorption in the absence of changes in renal hemodynamics. We chose reflex interventions as opposed to renal denervation to decrease efferent RSNA more physiologically. Activation of left atrial cardiopulmonary receptors (Karim et al. 1972) and stellate ganglion stimulation (Takeuchi et al. 1968) are both known to reflexly decrease efferent RSNA. Prosnitz and DiBona (1978) demonstrated that stellate ganglion stimulation produced reversible decreases in efferent RSNA which were associated with increases in urinary flow rate and sodium excretion in the absence of changes in renal perfusion pressure, renal blood flow, or glomerular filtration rate; thus, renal tubular sodium reabsorption decreased. These findings confirmed and extended the earlier observations of Gilmore (1964) and Takeuehi et al. (1968). With respect to the issue of reflex control of renal sodium and water handling by atrial mechanoreceptors, two seemingly disparate opinions exist. Goetz et al. (1975, 1979) believe that "the left atrial volume receptor hypothesis adds little to our current understanding of the regulation of extracellular fluid balance," that "the case for the left atrial volume receptor hypothesis has been built largely on indirect evidence," and that there is insufficient evidence for the atrial receptors to "be singled out for special attention as volume receptors that influence renal function." However, equally vigorous opposing views have been expressed by Gilmore and Zucker (1975), Gauer and Henry (1976) and Kappagoda (1979). Some portion of the controversy relates to conceptual differences between the various investigative groups. Goetz et al. (1975) identify the concept of reflex volume regulation with atrial receptors, antidiuretic hormone (ADH), and renal water excretion. However, as presented by Gauer and Henry (1976), the concept of reflex volume regulation requires three things: first, a well-defined compliance of the low pressure system relating blood volume to filling pressure; second, appropriate receptor networks in the walls of the low pressure system responsive to changes in wall tension and discharging in appropriate areas of the central nervous system; and third, related efferent neurohumoral mechanisms which control thirst, renal water and sodium excretion, and redistribution of the extracellular fluid volume as the major regulators of the plasma volume. Recent studies by Epstein (1978) indicate that water immersion produces a central volume stimulus with engorgement of the intrathoracic circulation which leads to a natriuresis and a diuresis. Similar findings are observed after The Functions of the Renal Nerves 125 lower body positive pressure in conscious animals (Kass et al. 1980). Thus, this appropriate homeostatic response is consistent with the view that central intrathoracic volume receptors are part of the afferent limb of a reflex volume-regulating system whose efferent limb involves changes in renal water and sodium excretion. Several recent studies deal with the left atrial volume receptor mechanism. Linden et al. (1979) demonstrated that the magnitude of the decrease in efferent RSNA during left atrial receptor stimulation was not influenced by changes in carotid sinus pressure. Using differential cooling of the cervical vagi, it has been shown that the reduction in efferent RSNA during distension of balloons in the left pulmonary vein-atrial junction, the left atrial appendage, and the left atrium and the accompanying increase in urinary flow rate are mediated solely by the Paintal-type atrial receptors which discharge into the myelinated fibers in the vagi (Linden et al. 1980; Sivananthan et al. 1981). As noted above, controversy exists with respect to the role of ADH in the diuretic response (i.e., increased urinary flow rate) to left atrial receptor stimulation. Goetz et al. (1975) suggested that the use of more precise, specific, and sensitive radioimmunoassay methods for measurement of plasma ADH concentrations might provide more reliable information. De Torrente et al. (1975) demonstrated that left atrial balloon inflation increased left atrial pressure, decreased urinary osmolality, increased urinary flow rate, and decreased plasma ADH concentration as measured by a radioimmunoassay method; a positive free water clearance was not observed. Renal perfusion pressure was controlled and there were no significant alterations in systemic or renal hemodynamics. The observed changes were completely reversible on deflation of the left atrial balloon. In steroid-replaced, hypophysectomized dogs receiving a constant intravenous infusion of ADH, left atrial balloon inflation produced similar increases in left atrial pressure but there were no associated changes in urinary osmolality or flow rate. These authors concluded that suppression of ADH release is the primary mechanism whereby increases in left atrial pressure cause an increase in urinary flow rate. These experiments have been criticized on the basis of the failure to observe a positive free water clearance and because, based on calculations using ADH bioassay techniques, a greater fall in plasma ADH concentration than observed would be needed to account for the increase in urinary flow rate (Kappagoda 1979). However, since urinary flow rate increased in the presence of unchanged urinary solute excretion and osmolar clearance in the study by de Torrente et al. (1975), it seems clear that the increase in urinary flow rate may be accounted for by the measured decrease in plasma ADH concentration. Furthermore, as extensively discussed by de Torrente et al. (1975) the ADH radioimmunoassay employed in their study was characterized by greater precision, specificity, and sensitivity than those ADH 126 G.F. DiBona

bioassay methods previously employed to assess the role of ADH in the diuretic respone to left atrial receptor stimulation in intact dogs (Kappa- goda et al. 1974) and dogs with destruction of the posterior pituitary (Kappagoda et al. 1975). With regard to the study by Kappagoda et al. (1975), in which electrical cauterization of the pituitary gland was used in an effort to abolish the diuretic response to left atrial receptor stimulation, several points should be noted. Previous studies have shown that as little as 7% of the hypothalamoneurohypophyseal tract is sufficient to prevent the development of diabetes insipidus (Heinbecker and White 1941). On histological examination at least one of the four dogs had incomplete ablation of the pituitary gland by electrical cauterization, and in this animal the area of destruction was actually outside the region of the pituitary gland (Kappa- goda et al. 1975). Moreover, plasma concentrations of ADH (measured in two of the four dogs, one having incomplete hypophysectomy) were not detectable by their bioassay even though histological examination revealed incomplete hypophysectomy. This result again raises questions concerning the sensitivity of ADH bioassay technique used, and perhaps offers an explanation why this group has been unable to detect a decrease in plasma ADH concentration during left atrial receptor stimulation using this same ADH bioassay technique (Kappagoda et al. 1974). While Ledsome and Linden (1968) have shown that the diuretic response to left atrial balloon inflation with mitral obstruction was 2.7 times control urine flow, whereas that to left pulmonary vein-atrial junction balloon inflation with pulmonary vein distension was 1.5 times control urine flow, statistical analysis of this difference was not presented and there were no other detectable differences in the renal responses to these two stimuli (Kappagoda et al. 1974). These conflicting views on the role of ADH in the diuretic response to left atrial receptor stimulation cannot be ascribed to different techniques of left atrial receptor stimulation, since inflation of a balloon within the left atrium was used by both de Torrente et al. (1975) and Kappa- goda et al. (1974, 1975). In addition, Thames and Schmid (1979) have recently demonstrated, using ADH radioimmunoassay techniques, that cardiopulmonary receptors with vagal afferents tonically inhibit the secretion of ADH. Kappagoda et al. (1979a) have recently described an as yet unidentified circulating humoral diuretic agent which is released during left atrial receptor stimulation. Dog plasma samples obtained during control periods and periods of left atrial receptor stimulation were applied to the Malphi- gian tubules of Rhodnius prolixus. Tubules suspended in dog plasma samples obtained during left atrial receptor stimulation secreted less fluid than when suspended in dog plasma samples obtained during control periods. Cutting or cooling the cervical vagi abolished these differences along with The Functions of the Renal Nerves 127 the diuretic response to left atrial receptor stimulation. It was suggested that left atrial receptor stimulation resulted in a release of a circulating humoral diuretic agent which is responsible for the increase in urinary flow rate. Further studies from the same group (Knapp et al. 1980) examined the possibility that either angiotensin II or bradykinin were involved in the diuretic response to left atrial receptor stimulation. The diuretic response was unaffected by administration of angiotensin-converting enzyme inhibitor. Furthermore, neither angiotensin II nor bradykinin significantly influenced the rate of secretion of Malphigian tubules of Rhodnius prolixus. Therefore, angiotensin II and bradykinin are unlikely humoral mediators of the diuretic response to left atrial receptor stimulation. Further studies employing ADH radioimmunoassay techniques as well as identification of substances of mammalian origin which inhibit secretion of the malphigian tubules are required to assess the relative contributions of circulating humoral substances (ADH, others) to the diuretic response during left atrial receptor stimulation. The mechanism of the associated natriuretic response to left atrial receptor stimulation has been examined in further detail. Prosnitz and DiBona (1978) showed that activation of left atrial cardiopulmonary receptors produced a reversible decrease in efferent RSNA which was associated with an increase in urinary flow rate and sodium excretion in the absence of changes in renal perfusion pressure, glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow (Figs. 13, 14). Bilateral cervical vagotomy abolished the decrease in efferent RSNA and the diuretic and natriuretic response to left atrial receptor stimulation.

130120 MAP mmHg 110 100 90LRpp t t I 3O LAP 20 I mmHg 10 0 150 F

beats/rain 130F Fig. 13. Effect of left atrial balloon in- 120 ~- flation on hemodynamic measurements

and efferent renal sympathetic nerve 8 activity in anesthetized dogs. MAP, 7 mean arterial pressure; renal RPP, Hz 6 perfusion pressure; LAP, left atrial pressure; heart rate; C, control; HR, N=7 E, experimental; R, recovery. (Prosnitz and DiBona 1978) 128 G.F. DiBona

Cin 25[ ml/min 20 Fig. 14. Effect of left atrial balloon inflation on renal function in anesthetized dogs. Cin, inulin clearance; RBF, renal blood ml/min flow; V, urinary flow rate; UNaV, urinary 200 L sodium excretion; C, control; E, experimental; R, recovery. (Prosnitz and DiBona V 2"0 I 1978) ml/min 1.5

1.0 140

120

UNaV 100 ~Eq/min 8O

6O N=7 I I I C E R

Infusion of exogenous ADH abolished the diuretic response, whereas the decrease in efferent RSNA and the natriuretic response to left atrial receptor stimulation were preserved. It was suggested that left atrial receptor stimulation produces a reflex whose afferent limb is in the vagus nerves and whose efferent limb for the diuretic response is suppression of ADH release and for the natriuretic response is a suppression of efferent RSNA. Kappagoda et al. (1979b) have examined the effect of renal denervation on the diuretic and natriuretic response to left atrial receptor stimulation. Whether the left atrial receptors were stimulated by large balloons in the left atrium or small balloons in the left pulmonary vein-atrial junction and the left atrial appendage, both the diuretic and natriuretic responses were significantly attenuated in the denervated kidney as compared to the innervated kidney in the same dog. Chapman et al. (1971), comparing the innervated and denervated kidney in the same dog, also demonstrated that the diuresis and natriuresis occurring in response to left atrial receptor stimulation were dependent on intact renal innervation. As reviewed by Kinney et al. (1974), paroxysmal atrial tachyarrhthmia in man is associated with a diuresis and natriuresis which is due to adecrease in renal tubular sodium and water reabsorption, possibly at the level of the proximal tubule. Experimental studies in animals using cardiac pacing techniques have also demonstrated diuretic and natriuretic responses, but these responses have been said to be mediated by sinoaortic baroreceptors and to be independent of changes in bioassayed plasma ADH concentrations (Goetz and Bond 1973) or dependent on changes in plasma The Functions of the Renal Nerves 129

ADH concentration mediated by left atrial receptors with vagal afferents (Boykin et al. 1974; Grossman et al. 1974). Kinney et al. (1974) have pointed out that the uniformly observed natriuretic response in patients cannot be completely explained by changes in plasma ADH concentrations. La Grange and Mitchell (1978) used left atrial pacing in anesthetized dogs and showed that the increased left atrial pressure was accompanied by a diuresis, natriuresis, and kaliuresis, in the absence of any changes in renal perfusion pressure or glomerular filtration rate; renal plasma flow decreased. Surgical or pharmacological (phenoxybenzamine) renal denervation blocked the excretory responses. Thus, these studies support the hypothesis that the diuresis and natriuresis of paroxysmal atrial tachyarrhythmia are due to a cardiorenal reflex involving left atrial receptors with vagal afferents and efferent RSNA. Although Mills and Osbaldiston (1968) and Stitzer and Malvin (1975) did not observe a diuretic or natriuretic response to right atrial receptor stimulation via balloon inflation, Kappagoda et al. (1973) clearly demonstrated increases in urinary flow rate (18%-34%) and sodium excretion (15%) during distension of balloons in either the right atrial appendage or superior vena cava-atrial junction. The responses were reversibly attenuated by cooling the fight cervical vagus. In conscious dogs, Goetz et al. (1981) demonstrated that fight atrial epicardial receptor anesthesia produced reversible decreases in urinary flow rate and sodium excretion which were independent of changes in plasma ADH or renin concentrations. The effects of left atrial receptor stimulation on the renal excretion of water and sodium in conscious unanesthetized dogs has been studied extensively by Reinhardt, Kaczmarczyk, and colleagues (Reinhardt et al. 1980a, b; Kaezrnarezyk et al. 1980). These workers have demonstrated that increasing left atrial pressure by constricting the mitral valve orifice with an implanted purse string suture increases urinary flow rate and sodium excretion independent of changes in renal perfusion pressure, glomerular filtration rate, or renal blood flow. Although they found that the natriuretic response to increasing left atrial pressure was not affected by renal denervation, the natriuretic response to ingestion of a sodium- rich meal which produced a comparable rise in left atrial pressure was abolished by renal denervation (Simgen et al. 1979). These disparate results may be explained by the experimental design which, rather than comparing the responses of an innervated and denervated kidney within the same dog to either intervention, studied the responses of both kidneys to either intervention before and after bilateral renal denervation. The effect of cardiac denervation on the diuretic and natriuretic responses to left atrial receptor stimulation has been studied by several groups. Using "pharmacological denervation" of both heart and kidney (bretylium, atropine, atenolol), Linden and Sreeharan (1979) showed that 130 G.F. DiBona

the natriuretic response to left atrial receptor stimulation was abolished. Reinhardt et al. (1980a, b), in conscious unanesthetized dogs, demonstrated that both the diuretic and natriuretic responses to left atrial receptor stimulation were abolished by total cardiac denervation. Fater et al. (1980), working with Goetz, have also demonstrated that total cardiac denervation abolished the diuretic and natriuretic response to left atrial balloon inflation. In contrast to the earlier views expressed by Goetz and colleagues (1975), these authors now state that "the diuresis elicited by inflating a balloon in the left atrium is mediated by a reflex arising from cardiac receptors" (Fater et al. 1980), and "the diuresis elicited by increasing left atrial pressure with a balloon is reflexly elicited from left atrial receptors'" (Sehultz et al. 1980). It should be noted that left atrial receptor stimulation does not produce a diuretic or natriuretic response in the monkey (Gilmore and Zucker 1978; Cornish and Gilmore 1981), which is probably explained by the fact that their left atrial receptors are substantially less sensitive than those in the dog (Zueker and Gilmore 1975). These several observations indicate that left atrial receptor stimulation (increased left atrial pressure due to left atrial balloon inflation) produces an increase in urinary flow rate and sodium excretion independent of systemic or renal hemodynamic changes. This neurogenic reflex mechanism is dependent on an afferent limb involving unencapsulated end-organs in the left atrial endocardium served by myelinated vagal fibers. The efferent limb involves a decrease in efferent RSNA which totally accounts for the increase in urinary sodium excretion and partly accounts for the increase in urinary flow rate. The possibility remains that an as yet unidentified circulating humoral agent, in addition to suppression of ADH, contributes to the increase in urinary flow rate but not sodium excretion. Activation of other cardiac receptors has been demonstrated to produce reflex changes in renal water and sodium excretion. Lazzara et al. (1970) showed that coronary sinus occlusion in dogs led to increases in urinary flow rate, glomerular filtration rate, and renal blood flow at constant renal perfusion pressure; these reponses were absent in the denervated kidney. Wennegren et al. (1976), in the cat, used direct electrical stimulation to activate cardiac unmyelinated vagal fibers which mainly originate from ventricular receptors. At constant renal perfusion pressure, there were increases in urinary flow rate, sodium excretion, and renal blood flow; data on glomerular filtration rate were not reported. Similar diuretic, natriuretic, and renal vasodilatory responses were seen with stimulation of either cardiac or aortic nerves or intra-arterial administration of papaverine. Thus, the excretory responses were most likely mediated by changes in renal hemodynamics, probably including an increase in glomerular filtration rate, as opposed to a specific decrease in renal tubular The Functions of the Renal Nerves 131 sodium reabsorption. Clinically, patients with acute myocardial infarction and moderate left ventricular failure have higher levels of glomerular filtration rate and dally excretion rates of water and sodium than those patients without left ventricular failure or with pulmonary edema (Bennett and Keddie 1974;Effendigilet al. 1975;Bennett et al. 1977, 1979). In view of the extensive sensory functions of the liver (Sawchenko and Friedman 1979), hepatorenal reflex responses have been described. Liang (1971) observed that increases in hepatic portal venous pressure produced increases in urinary flow rate and chloride excretion which were associated with increases in renal plasma flow and glomerular filtration rate; these responses were reversibly abolished by application of local anesthetics to the renal neurovascular pedicle. Niijima (1976) provided evidence that this was a neurogenic reflex involving efferent RSNA by demonstrating that portal vein occlusion decreased efferent RSNA in anesthetized rabbits. In our laboratory, we have observed (unpublished observations) that portal vein occlusion in anesthetized dogs (20 tests in 4 dogs) decreased efferent RSNA from 9.8 -+ 0.5 to 7.4 -+ 0.4 Hz in association with a decrease in mean arterial pressure from 134 -+ 5 to 125 -+ 5 mmHg; on release of the portal vein occlusion, efferent RSNA returned to 9.4 -+ 0.4 Hz and mean arterial pressure returned to 137 -+ 4 mmHg. Shock avoidance has been employed as a generalized environment stress which probably increases sympathetic activity. In conscious dogs, shock avoidance decreases urinary flow rate and sodium excretion without changing glomerular filtration rate, indicating an increase in renal tubular sodium and water reabsorption (Grignolo et al. 1980). This response was abolished by the intravenous administration of propranolol (Koepke et al. 1981). To determine whether efferent renal nerves and/or renal/3-adrenoceptors are involved in this response, studies must be performed in dogs with renal denervation and renal arterial administration of ~-adrenoceptor antagonists.

4.2.4 Characterization of Catecholamine Receptors The subject of catecholamines and sodium excretion, in terms of characterization of the renal tubular adrenoceptors involved, has been reviewed by Baines and Morgunov (1980). Morel (1981) and Morel et al. (1981) identified catecholamineosensitive adenylate cyclase receptors in micro- dissected segments of the rabbit nephron./~-Adrenoceptors were identified in the distal convoluted and cortical collecting tubule but not in the proximal convoluted or straight tubule, a-Adrenoceptors were not found in the distal convoluted tubule or the cortical collecting tubule and observations were not reported for the proximal tubule. Besarab et al. (1977), in the isolated perfused rat kidney, showed that the simultaneous administration 132 G.F. DiBona

of norepinephrine and phenoxybenzamine decreased fractional sodium excretion without changing glomerular filtration rate or perfusion medium flow. The combination of norepinephrine and propranolol did not affect fractional sodium excretion. However, both phenylephrine and isoproterenol, when given alone, also decreased fractional sodium excretion without affecting glomerular filtration rate or perfusion medium flow. The results were interpreted as showing that humoral ~-adrenoceptor stimulation increases renal tubular sodium reabsorption; however, the phenylephrine response is at variance with this view. Pastoriza (1979) performed simultaneous microperfusion experiments in the proximal convoluted tubule and peritubular capillaries of anesthetized rats. When added to the peritubular capillary perfusate, norepinephrine increased and phentolamine decreased net fluid reabsorption. The results were interpreted as showing that humoral stimulation of ~-adrenoceptors located at the basolateral membrane enhances proximal tubular fluid reabsorption by a direct tubular action. In isolated perfused rabbit cortical collecting tubules, isoproterenol in the bath decreases the negative potential difference and increases net chloride reabsorption (Iino et al. 1979; Iino and Brenner 1979). In the isolated perfused mouse medullary thick ascending limb of Henle's loop, isoproterenol and norepinephrine (bath) increased the lumen positive potential difference and chloride effiux; this effect was inhibited by propranolol (Polhemus and Hall 1980). BeUo-Reuss (1980) has studied the effect of catecholamines on fluid reabsorption by the isolated perfused superficial proximal convoluted and straight portions of the rabbit renal tubule. Norepinephrine, at concentrations of 10 -7 M or higher, enhanced fluid reabsorption in the proximal convoluted but not the straight tubule; it was inactive when added to the luminal perfusion. A similar stimulatory effect was seen with isoproterenol in the presence of phentolamine. The effects of both norepinephrine and isoproterenol were blocked with propranolol. Norepi- nephrine, in the presence of propranolol, produced a slight decrease in fluid reabsorption. These results were interpreted as demonstrating that humoral/3-adrenoceptor stimulation increases and ~-adrenoceptor stimulation decreases fluid reabsorption in the rabbit superficial proximal convoluted tubule. However, the effect of a pure ~-adrenoceptor agonist such as phenylephrine or methoxamine was not evaluated. Using simultaneous proximal tubular and peritubular capillary microperfusion techniques in the rat, Chan (1980a, b) showed that norepinephrine in the peritubular capillary perfusate increased proximal tubular water and bicarbonate reabsorption through stimulation of peritubular a-adrenoceptors (phenoxybenzamine block). Hollingsead and Willis (1980) gave renal arterial infusions of/~-adrenoceptor agonists or antagonists during continuous renal arterial infusion of phentolamine to anesthetized The Functions of the Renal Nerves 133 rabbits. The 9-adrenoceptor agonists or antagonists produced no change in mean arterial pressure, heart rate, urinary flow rate, glomerular filtration rate, or renal plasma flow. 9-Adrenoceptor antagonists (propranolol) increased and 9-adrenoceptor agonists (norepinephrine, isoproterenol) decreased fractional sodium excretion. These results were interpreted as showing that humoral fl-adrenoceptor stimulation increases and blockade decreases renal tubular sodium reabsorption. Previous studies in our laboratory indicate that renal tubular a-adrenoceptors mediate the direct increase in renal tubular sodium reabsorption observed following either direct electrical renal nerve stimulation (Zambraski et al. 1976) (Fig. 8) or physiological reflex activation of the efferent renal sympathetic nerves (Zambraski et al. 1967b; DiBona and Johns 1980)(Figs. 11, 12). More recent studies in our laboratory (DiBona and Osborn 1981) demonstrate that neither renal 9-1,2 (D,L-propranolol) nor fl-1 (atenolol) adrenoceptor blockade affected the antinatriuretic response to low level renal nerve stimulation (Fig. 15). In contrast, renal a-adrenoceptor blockade with phentolamine, phenoxybenzamine or, prazosin (a-l) markedly inhibits this response (Fig. 15).

(4) (10) (11) (~0/ (6) D,L-PROP Atenolo[ Phentol POB Prazosin - oi I 5 -2o I I = I i <~ -3C I

-4C [ , -50 7 " [-"]Control RNS I [~lDr ug RNS F NS NS p<0.01 p<0.005 p

With respect to dopamine, clearance studies indicate that exogenous dopamine is natriuretic (Goldberg and Weder 1980). Intravenous infusion of dopamine in the cat increases urinary flow rate, sodium, potassium, and chloride excretion without affecting mean arterial pressure, glomerular filtration rate, renal blood flow, or efferent RSNA; a direct action of dopamine to decrease renal tubular reabsorption was postulated (Wassermann 134 G.F. DiBona et al. 1980). However, rat renal micropuncture studies indicate that dopamine increases proximal tubular sodium and water reabsorption (Greven and Klein 1977), whereas dopamine in the bathing medium decreased fluid reabsorption in the isolated perfused proximal straight tubule of the rabbit, a segment unresponsive to norepinephrine (Higashi and Bello-Reuss 1980). Arruda and Sabatini (1980) have reported that endogenously formed dopamine inhibits water transport in the isolated toad bladder. A recent review of the literature pertaining to dopamine and its effect on urinary sodium excretion concludes that there is insufficient evidence to support a direct action of dopamine on renal tubular sodium reabsorption (Gold- berg and Weder 1980). The precise characterization of the adrenoceptor involved in directly influencing renal tubular sodium reabsorption in response to changes in efferent RSNA has not been achieved with in vitro studies employing humoral adrenergic agonists and antagonists. It is possible that the results of such in vitro studies employing humoral adrenergic agonists and antagonists might not be relevant to the characterization of the adrenoceptor mediating the changes in renal tubular sodium reabsorption observed after physiological alteration of efferent RSNA in vivo, either directly or reflexly.

4.2.5 Summary Bidirectional alterations in efferent RSNA, produced either directly (renal nerve stimulation, renal denervation) or by activation of physiological reflexes (carotid sinus baroreceptors, left atrial mechanoreceptors), cause parallel changes in renal tubular sodium and water reabsorption which are directly mediated by adrenergic nerve terminals in contact with renal tubular epithelial cells. Renal hemodynamic factors, peritubular physical forces, and circulating humoral substances are not involved. The proximal tubule has been identified as one site of action for this neural control mechanism for solute and water transport. The efferent renal sympathetic nerves are participants in the efferent limb(s) of the mechanism(s) involved in the avid renal sodium retention of certain edema-forming conditions as well as the normal physiological response to dietary sodium deprivation. This neural control mechanism" is operative in the conscious unanesthetized animal. Current evidence favors the view that the mechanism operates via renal tubular a-adrenoceptors, although improved ability to characterize renal tubular epithelial cell membrane catecholamine receptor anatomy will provide further information on this issue. The Functions of the Renal Nerves 135

4.3 Control of Renal Hormonal Systems

This section will deal with the effects of efferent RSNA on the renal production of renin, prostaglandin, and kallikrein.

4.3.1 Renin Three primary mechanisms are involved in the release of renin from the juxtaglomerular granular cells of the kidney: the renal vascular barorecep- tot mechanism, the macula densa receptor mechanism, and the direct sympathetic neural control mechanism. ThEse mechanisms have been the subject of several recent review (Davis and Freeman 1976; Reid et al. 1978; Fray 1980). Specifically, the role of the central nervous system in influencing renin secretion via the efferent renal sympathetic nerves and catecholamines has been summarized in detail by Reid et al. (1978). In addition, the subject of pharmacological alteration of renin release has been comprehensively reviewed (Keeton and Campbell 1980). Therefore, this section will focus on more recent contributions.

4.3.1.1 Direct Stimulation of the Renal Nerves. In accord with La Grange et al.'s (1973) early findings, RNS, at an intensity which does not change renal hemodynamics but decreases urinary sodium excretion, increases renin release (Taher et al. 1976; Zambraski and DiBona 1977; Kopp 1980). It is possible that the associated decrease in urinary sodium excretion might have contributed to the renin release via activation of the macula densa receptor mechanism. However, Osborn et al. (1981a) have recently reported that there is a level of RNS (0.5 Hz) which reversibly increases renin release in the absence of changes in renal perfusion pressure, renal blood flow, glomerular filtration rate, or urinary sodium excretion. In the absence of input stimuli to either the baroreceptor or the macula densa receptor, this renin release derives from direct renal nerve stimulation of the juxtaglomerular granular cells.

4.3.1.2 Reflex Stimulation of the Renal Nerves. As recently reviewed by Thames (1978), Thoren (1979), and Donald and Shepherd (1980), the interaction between the high pressure (carotid and aortic) and low pressure (cardiopulmonry) baroreceptors can significantly influence renin release via modulation of efferent RSNA. Renin release increases when there is a decrease in the inhibitory activity of any one of the three peripheral receptor systems (carotid, aortic, cardiopulmonary) if such withdrawal does not alter the activity of the other two. Vagally innervated cardiopulmonary receptors exert a tonic inhibition of renin release and are 136 G.F. DiBona

more sensitive to modest decreases in blood volume than are carotid baroreceptors. With respect to the effects of carotid sinus hypotension on renin release, as indicated by Donald (1979), only in those studies in which the animals were vagotomized and in which renal perfusion pressure was held constant did consistent and significant increases in renin release occur. Similar findings have been observed in conscious unanesthetized dogs (Rocchini and Barger 1979; Gross et al. 1981b). The renin release response to bilateral carotid occlusion is associated with decreased renal blood flow in anesthetized dogs and cats (Jarecki et al. 1978; Powis and DonaM 1979; Arnmons et al. 1980). Both these responses to carotid occlusion are mediated via efferent RSNA. This has been demonstrated by blockade of the renin release response with renal denervation (Jarecki et al. 1978) or propranolol (Powis and DonaM 1979; Amrnons et al. 1980; Gross et al. 1981). Furthermore, Gross et al. (1980) have demonstrated an increase in efferent RSNA in conscious dogs after carotid occlusion. In the study by Powis and Donald (1979)phenoxybenzamine abolished the decrease in renal blood flow produced by carotid occlusion but not by suprarenal aortic constriction. Mursch and Bishop (1980) studied the renin release response to vagal cold block before and after nonhypotensive hemorrhage in conscious dogs. Vagal cold block increased mean arterial pressure and heart rate but decreased renin release without changing renal blood flow before and after nonhypotensive hemorrhage. Thus, the increase in mean arterial pressure was sufficient to inhibit the renin secretory response to reflex increases in efferent RSNA, probably acting through carotid sinus or renal vascular baroreceptors. In a recent series of studies, Stella and colleagues (Stella et al. 1978a,b; Dampney et al. 1979) utilized head-up tilt in anesthetized cats to study the interaction of vagal and sinoaortic reflexes in the postural control of circulation and renin release. Bilateral cervical vagotomy did not affect the hemodynamic change to posture but markedly reduced the renin release response from the innervated kidney. After sinoaortic denervation, a marked and sustained arterial hypotension occurred during tilting and the postural increase in renin release from the denervated kidney. It was concluded that maintenance of arterial pressure during tilting is mainly due to sinoaortic reflexes, whereas vagal reflexes are mostl3~ responsible for the postural increase in renin release. However, DiBona et al. (1981) have recently shown that bilateral cervical vagotomy does not affect the antinatriuretic (DiBona and Johns 1980) or renin response to 60 ° head-up tilt in anesthetized dogs. The renin release response to head-up tilting has been examined in conscious dogs (Grand]ean et al. 1978). Head-up tilt increased renal venous plasma renin activity (PRA) from the innervated but The Functions of the Renal Nerves 137 not the denervated kidney. After furosemide administration, renal venous PRA increased bilaterally but the response to the innervated kidney exceeded that of the denervated kidney. In the nonhypotensive phase of progressive slow hemorrhage, renal venous PRA increased bilaterally but the response of the innervated kidney exceeded that of the denervated kidney. When hypotension supervened, renal venous PRA increased equally from both kidney. The effect of peripheral venous pooling (thigh cuff) on PRA was studied in normal human subjects and four bilaterally nephrectomized patients with functioning renal transplants (Kiowski and Julius 1978). In normal human subjects, increases in PRA were associated with decreases in right atrial pressure, cardiopulmonary blood volume, and cardiac output while arterial pressure was unchanged. The PRA response was abolished by propranolol and was attenuated or absent in the four patients with recent renal transplants (3-7 months before study). It was concluded that this reflex-mediated increase in PRA arose from stimulation of cardiopulmonary receptors. Fisher and Malvin (1980) examined the mechanism of the decrease in renin release produced by intravascular volume expansion. In anesthetized dogs they found the decrease in renin release produced by isotonic iso-oncotic dextran administration to be unaffected by bilateral cervical vagotomy or by surgical renal denervation. They concluded that the renin release response to intravascular volume expansion was independent of the vagi or the renal nerves and that the renin-angiotensin system was not part of the efferent limb of the cardiopulmonary reflex during adjustments to changes in blood volume. However, Holdaas and DiBona (1981) demonstrated that the renin release response to nonhypotensive hemorrhage in sodium-replete dogs was abolished by preventing the associated decrease in left atrial pressure by inflating a balloon in the left atrium (Fig. 16). Livnat and Zehr (1980) have shown that left circumflex coronary artery occlusion reflexly inhibits the renin release and renal vasoconstrictor response to nonhypotensive hemorrhage in sodium-depleted dogs. The renin release and renal vasoconstrictor responses were dependent on intact renal innervation and the inhibitory effect of left circumflex coronary artery occlusion was dependent on intact vagi. Continuous positive pressure ventilation decreases intrathoracic blood volume causing reflex decreases in renal function and increases in renin release which are mediated by the renal nerves (Fewell and Bond 1979;Bond and Lightfoot 1981). Zimmerman and Ganong (1980) recently showed that 5-hydroxytryptophan and L-tryptophan act on the central nervous system to produce an increase in PRA which is mediated via efferent RSNA and occurs without an associated increase in sympathetic output to the heart or blood vessels. Since the PRA response was abolished by administration of agents which 138 G.F. DiBona

Fig. 16. Effect of nonhypotensive LAP 3 hemorrhage and left atrial balloon mmHg 2 inflation on renal function and renin 1 release (RR) in anesthetized dogs. 0 LAP, left atrial pressure; RPP, renal RPP 90 perfusion pressure; RBF, renal blood mrnHg 80 flow; C control; H hemorrhage; R, 70 recovery. (Holdaas and DiBona 1981) RBF 120 ml/min 90 6O E

RR 15 pg/rnin 10

0 ~=6, I I I I C H R H+ LAP~ R+LAP~

inhibit central nervous system aromatic amino acid decarboxylase, it was suggested that the release of 5-hydroxytryptamine (serotonin) within the central nervous system was responsible for the observed response.

4.3.1.3 Role of ~-Adrenoceptors in the Neural Control of Renin Release. Taher et al.'s (1975) demonstration that the renin release produced by low level renal nerve stimulation was blocked by propranolol suggested that renin release solely derived from neural stimulation ofjuxtaglomeru- lar granular cells (i.e., no renal hemodynamic changes) was mediated by fl-adrenoceptors. However, since urinary sodium excretion decreased in these studies, it remained possible that activation of the macula densa mechanism contributed to the observed renin release response. Recently Osborn et al. (1981 a) demonstrated that renal nerve stimulation at 0.5 Hz increases renin release without affecting renal perfusion pressure, renal blood flow, glomerular filtration rate, or urinary sodium excretion. In the absence of changes in input stimuli to either the baroreceptor or macula densa receptor, the observed renin release derives from neural stimulation of juxtaglomerular granular cells. The renin-release response was completely abolished by renal ~-1 adrenoceptor blockade with atenolol (Fig. 17), while it was unaffected by renal ~-2 adrenoceptor blockade with butoxamine. Using a slightly higher level of RNS which produced a 5% decrease in renal blood flow and a 50% decrease in urinary sodium excretion, Kopp et al. (1980a) have recently shown that the renin release response was The Functions of the Renal Nerves 139

Fig. 17. Effect of renal t3-1 adreno- ~5o r z z~ ceptor blockade with atenolol on (mrnHg)AP 125I renal function and renin secretion 100'- rate (RSR) responses to low level 250 F renal nerve stimulation (0.5 Hz) in RBF -(30/ anesthetized dogs. AP, arterial (ml/min) Z ~- t {-----{ pressure; RBF, renal blood flow; 150 L GFR, glomerular filtration rate; GFR 40[ F___ ,~ __-} UNaV, urinary sodium excretion; (ml/min) 30 C, control; RNS, renal nerve 200 r stimulation; R, recovery; A TN, u.:v, ~ool- F_~ I .= atenolol. (Osborn et al. 1981a) tp='-q/m n) 0L

RSR 200[ (ng/min) 100[ 0L ATN RNS F~ Atenolol (2 J~g/kg/min)

almost completely abolished by a different/3-1 adrenoceptor antagonist, metoprolol, given intravenously. Using a higher level of RNS which produced a 30% decrease in renal blood flow in cats, Johns (1981) demonstrated that the renin release response was inhibited by the 13-1 adrenoceptor antagonist, atenolol, but unaffected by the/3-2 adrenoceptor antagonist, ICI 118,551. Taken together, these studies indicate that renin release solely due to renal nerve stimulation, i.e., no change in input stimuli to either the baroreceptor or macula densa receptor mechanisms, is mediated by 13-1 adrenoceptors located on the juxtaglomerular granular cells. Although renin release can be induced by exogenous 13-adrenoceptor agonists in vivo and vitro, the final step in activation of the juxtaglomerular granular cells may not be identical to the produced by neuronally released norepinephrJne. There may be differences in receptor location (vascular versus interstitial) and subtle, perhaps undetectable, differences in renal hemodynamics produced by exogenous adrenergic agonists that might differ from those produced by activation of the renal sympathetic nerves. It should be noted, however, that recent studies in conscious dogs by Himori et al. (1979, 1980) using isoproterenol and 13-1 or 13-2 adrenoceptor antagonist administration demonstrated that the isoproterenol- induced increase in PRA is due to activation of 13-1 adrenoceptors. In addition, both Kopp et al. (1981b) and Campbell et al. (1979) have shown that administration of prenalterol, a 13-1 adrenoceptor agonist, increases renin release in dogs (blocked by metoprolol) or increases PRA in rats, respectively. Using humoral stimulation of renal 13-adrenoceptors in 140 G.F. DiBona anesthetized dogs pretreated with indomethacin, Olson et al. (1980b) examined the renin release response to the nonselective /3-1//3-2 adrenoceptor agonist, isoproterenol, before and after either selective/3-1 adrenoceptor blockade with atenolol or nonselective/3-1//3-2 adrenoceptor blockade with sotalol. The renin release response to isoproterenol was unaffected by atenolol but was inhibited by sotalol. Although the results were interpreted as demonstrating that renal /3-2 adrenoceptor stimulation increases renin release, data from experiments employing a selective /3-2 adrenoceptor antagonist (e.g., butoxamine) were not presented. The issue of extrarenal /3-adrenoceptor mediation of renin release (Reid et al. 1972) has been restudied by Johnson et al. in conscious dogs (1979a, b). Intravenous infusion of epinephrine raised PRA considerably more than infusion of norepinephrine, whereas renal arterial infusion to produce similar renal arterial concentrations did not affect PRA; the PRA response was blocked by propranolol. The circulating concentrations of epinephrine achieved were less than those occurring after insulin administration of hemorrhage. It was concluded that circulating epinephrine in the physiological range plays a role in the control of PRA by activation of an extrarenal/3-adrenoceptor (Johnson 1979b). In a subsequent study the PRA response to infused epinephrine was shown to be independent of the renal nerves, changes in renal perfusion pressure, hematocrit, plasma potassium, and prostaglandin concentration (Johnson 1979a).

4..?.1.4 Role of ~-Adrenoceptors in the Neural Control of Renin Release. With respect to an inhibitory effect ~-adrenoceptor stimulation on renin release, clonidine, an a-adrenoceptor agonist, is known to decrease PRA, but this results from a centrally mediated decrease in efferent RSNA (Nolan and Reid 1978;Leavitt et al. 1980). However, other observations suggest that a-adrenoceptor stimulation increases renin release. Blair (1979) reported that intrarenal phenoxybenzamine suppressed renin release in anesthetized dogs with systemic/3-adrenoceptor blockade. Sub- sequently, Blair (1980) reported that both phenylepinephrine and methoxamine, given into the renal artery, increased renin release without affecting renal blood flow. However, both these studies were performed at a ~constant renal perfusion pressure of 90 mmHg, which engages the baroreceptor mechanism for renin release through autoregulatory renal vasodilatation. In addition, data on glomerular filtration rate and urinary sodium excretion were not reported, so that activation of the macula densa receptor mechanism cannot be excluded. Powis and Donald (1979) reported that renal ~-adrenoceptor blockade with phenoxybenzamine abolished the renin release response and the renal vasoconstrictor response to bilateral carotid occlusion. However, in all these studies the changes in renal neuroadrenergic activity increased renal vascular resistance and prob- The Functions of the Renal Nerves 141 ably decreased distal tubular delivery of sodium chloride. Thus, the neuroadrenergic stimuli used also altered the stimuli to the nonneuroadrenergic mechanisms for renin release. Olson et al. (1980a) reported that infusion of phenylephrine into the renal artery of denervated kidneys in #-adrenoceptor-blocked dogs decreased renal blood flow and urinary sodium excretion and increased renin release; only the renin release was blocked by indomethacin. In addition, no increase in renin release was seen when phenylephrine was infused into nonfiltering kidneys. They concluded that renal a-adrenoceptor activation led to a decrease in distal tubular sodium chloride delivery which stimulated the macula densa to release renin via a prostaglandin-dependent pathway. However, it is possible that the renal vasoconstriction produced by phenylephrine could lead to prostaglandin release (McGiff et al. 1972) and subsequent renin release independent of events occurring at the macula densa receptor. In addition, it is not known whether the nonfiltering kidney releases prostaglandins in response to infusion of a-adrenoceptor agonists. Recent studies by Osborn et al. (1982) serve to further define the role of 0~-adrenoceptors in the renin release response to RNS. RNS at 0.5 Hz increased renin release without changing renal perfusion pressure, renal blood flow, glomerular filtration rate, or urinary sodium excretion. This renin release, in the absence of changes in input stimuli to either the baroreceptor or the macula densa receptor, is due to neural stimulation of juxtaglomerular granular cells. Renal o~-adrenoceptor blockade with phentolamine did not affect the renin release response (Fig. 18), whereas phenoxybenzamine blocked the renin release. The doses of phentolamine and phenoxybenzamine were equipotent in reducing the renal vasoconstrictor responses to graded levels of RNS. Phenoxybenzamine did not affect the

AP 17SF mmHg 1501 ~ 125 =" ~" ] ~ 2oo F RBF 150~- ml/min 100 L GFR 40 E ~ I ml/min 30 ~--~ ~= ] 100 y ON V So L Fig. 18. Effect of renal 0~-adrenoceptor blockade with phentolamine on renal function and renin secretion rate (RSR) responses to low level ng/rninRSR 100i renal nerve stimulation (0.5 Hz) in anesthetized dogs. See Fig. 17 for 0|n:8 C RI~S I~ Phent RI~IS I~ abbreviations. PHENT, phentolamine. Phentolamine (Osborn et al. 1982) (2.0 pg/kg/rnir0 142 G.F. DiBona

15o[ Fig. 19. Effect of renal ol-adrenocep- AP 125- ~ ~ ~ =~ (mmHg) tor stimulation with methoxamine 100 FL on renal function and renin secretion rate (RSR) in anesthetized dogs. (ml/min) 150 100 t- Me th a, 0.05-0.10 ng/kg/min; Me th 2, 0.09-0.40 ng/kg/min; Meth3, 0.40- GFR (ml/mirO 35 2.0 ng/kg/min. See Fig. 17 for abbre- 30 * viations; METH, methoxamine. 1501- (Osborn et al. 1982) UNaV (pEq/rnin) 100~- t ~ "i* . 50 L

n=12 RSR '°° I (ng/min) 2001

I I I O~ C Meth 1 C Meth 2 Meth a renin release response to renal ~-adrenoceptor stimulation with isoproterenol. Renal a-adrenoceptor stimulation with methoxamine (Fig. 19) at doses which did not affect renal perfusion pressure, renal blood flow, glomerular filtration rate, or urinary sodium excretion did not change renin release. Infusion of higher doses of methoxamine which decreased renal blood flow and urinary sodium excretion increased renin release. It was concluded that renin release in response to direct neuroadrenergic stimulation of the juxtaglomerular granular cells without engagement of baroreceptor or macula densa receptor mechanisms is not mediated by intrarenal a-adrenoceptors. Phenoxybenzamine appears to affect the renin- release response to RNS through mechanisms dissimilar from phentolamine, which is in keeping with recent observations of Kalsner and Chan (1979) that these two compounds have different a-adrenoceptor antagonist properties. Isolated renal a-adrenoceptor stimulation (i.e., no baroreceptor or macula densa receptor engagement) does not increase or decrease renin release.

4.3.1.5 Role of Prostaglandins in Neural Control of Renin Release. There is a close interrelationship between renal hemodynamics, neuradrenergic tone to the kidney, and the renal production of renin and prostaglandin. Close intrarenal infusion of the prostaglandin precursor, arachidonic acid, increased PRA in rabbits, while inhibition of prostaglandin synthesis by indomethacin decreased it (Larsson et al. 1974). Renal artery constriction to decrease renal perfusion pressure resulted in increased renal secretion of PGE2 and PGF2~ (Dunn et al. 1978). Intrarenal infusion of PGE2 and PGI2 resulted in renal vasodilatation and renin release in propranolol- treated denervated nonfiltering kidneys (Gerber et al. 1979). Thus, renin release can be produced by prostaglandins in a baroreceptor-isolated kidney. Reduction of renal perfusion in renal venous PRA which was abol- The Functions of the Renal Nerves 143 ished by indomethacin (Data et al. 1978). Blackshear et al. (1979), in filtering kidneys, demonstrated that this was true only for pressure reductions within the autoregulatory range for renal blood flow; below that level renin release was not affected by prostaglandin synthesis inhibitors (Seymour and Zehr 1979). An increased release of prostaglandins following administration of ethacrynic acid was demonstrated by Williamson et al. (1976). Dietary sodium deprivation increases the renal release of prostaglandin, renin, and norepinephrine (Davila et al. 1978; Oliver et al. 1980b). A role for prostaglandins in macula densa-mediated renin release has been put for- ward by several workers. Olson et al. (1980c)infused papaverine into the renal artery of a denervated filtering kidney in /3-adrenoceptor-blocked dogs. In this preparation, the influence of circulating catecholamines, renal sympathetic nerves, and changing input from the renal vascular baroreceptor have been eliminated, thus leaving only the macula densa receptor mechanism operative. A reduction in renal perfusion pressure decreased urinary sodium excretion and increased renin release; only the increase in renin release was blocked by indomethacin. Both Francisco et al. (1980b) and Abe et al. (1980) have studied the prostaglandin dependence of renin release in response to stimulation of the macula densa receptor by dietary deprivation. In both studies, the increase in plasma renin activity occurring during dietary sodium deprivation was abolished by indomethacin. }Tun et al. (1977) have also reported decreased renin release by indomethacin during dietary sodium deprivation in anesthetized dogs. This inhibition occurred despite the fact that administration of indomethacin resulted in marekd changes in systemic and renal hemodynamics which would be expected to increase renin release as was observed by Opgenorth et al. (1980). In the study by De Forrest et al. (1980) indomethacin only reduced the renin release response to sodium deprivation in the presence of propranolol. Similar results were found by Frolich et al. (1976) in man. It is known that renal nerve stimulation at intensities which produce renal hemodynamic changes increases renal prostaglandin release (vide infra). Reflex activation of efferent RSNA by orthostasis increased PRA which was reduced by indomethacin (Rumpf et al. 1975). The role of prostaglandins in the PRA response to hemorrhage has been examined by Romero et al. (1976) in rabbits and Henrich et al. (1978) in dogs. While Romero et al. demonstrated a decrease of PRA response to hemorrhage by prostaglandin synthesis inhibitors, Henrich et al. found no inhibitory effect on PRA response by the durgs. The effects of hemorrhage on systemic and renal hemodynamics were not reported by Romero et al., but Henrich et al. reported decreases in mean arterial pressure, renal blood flow, and renin release. Indomethacin potentiated the renal hemodynamic ra~oonses to hemorrhage in the innervated kidney, which may have influ- 144 G.F. DiBona

enced the renin release per se. The complexity of the renin release response to hypotensive hemorrhage was later demonstrated by Henrieh et al. (1979). They showed that neither controlled renal perfusion pressure, propranolol, nor indomethacin alone could block the renin release response to hypotensive hemorrhage. However, the combination of controlled renal perfusion pressure and propranolol or the combination of propranolol and indomethacin abolished the renin release response to hypotensive hemorrhage. The combination of controlled renal perfusion pressure and indomethacin had no effect on the renin release response. Thus, their findings suggest that the renin release occurring during hypotensive hemorrhage is mediated by renal ~-adrenoceptors, by the renal baroreceptor mechanism, and possibly by the macula densa mechanism. The baroreceptor mechanism and probably the macula densa mechanism are prostaglandin mediated. Whether prostaglandins are involved in/3-adrenoceptor-mediated renin release has been examined by the use of ~-adrenoceptor agonists. Berl et al. (1979) and Johnson et al. (1979a) found no effect in dogs. However, in both studies administration of the drugs was associated with changes in renal hemodynamics although renal perfusion pressure was held constant in the study by Berl et al. In rats /3-adrenoceptor-mediated renin release produced by a/3-1 adrenoceptor agonist or by hypoglycemia was found to be reduced by indomethacin (Campbell et al. 1979; Campbell and Zimmer 1980). No measurements of renal hemodynamic or excretory function were reported. Using a model of hemorrhagic hypotension in anesthetized rats, Gerber et al. (1980) reported that the increase in plasma renin activity was partially blocked by propranolol or indomethacin when administered alone and completely inhibited by the combination. In adrenalectomized rats indomethacin administration completely inib- ited the increase in plasma renin activity following hemorrhagic hypotension. These data suggest that the ~-adrenoceptor- and prostaglandin- dependent pathways for renin release following hemorrhagic hypotension function independently, i.e., in parallel rather than in series. Further- more, the /3-adrenoceptor pathway requires intact adrenals, suggesting a role for circulating epinephrine in the renin release response to hemorrhagic hypotension. In addition, in adrenalectomized animals, the renin- releasing influence of the reflex increase in efferent RSNA occurring in response to hemorrhagic hypotension must be linked in series to the prostaglandin-dependent pathway for renin release. Using isolated rat glomeruli, Beierwaltes et al. (1980) showed that ~-adrenoceptor stimulation with isoproterenol stimulated renin release which was unaffected by pretreatment with mechlofenamate. Although renal nerve stimulation increases renal prostaglandin release, Kopp et al. (1980a) found that neither indomethacin nor diclofenac sodi- The Functions of the Renal Nerves 145 um, 5 mg/kg intravenously, affected the renin release response to a low level of direct renal nerve stimulation which produced slight changes in renal hemodynamics and urinary sodium excretion. However, Thames et al. (1980) found that intrarenal arterial administration of indomethacin abolished the renin release response to a low level of direct renal nerve stimulation which produced no changes in renal hemodynamics or urinary sodium excretion. Further studies using different doses of various prostaglandin synthesis inhibitors adminstered systemically or locally into the the kidney in conjunction with graded levels of direct renal nerve stimulation will be required to clarify the issue of whether neurally stimulated /3-adrenoceptor-mediated renin release is prostaglandin dependent.

4.3.1.6 Integrated Aspects of the Neural Control of Renin Release.There is considerable evidence that three primary mechanisms are involved in the control of renin release from the juxtaglomerular granular cells of the kidney. The first mechanism, direct sympathetic nervous control, is mediated by /3-1 adrenoceptors on the juxtaglomerular granular cells. The second, the renal vascular baroreceptor mechanism, responds to changes in wall tension in the afferent arteriole. The third, the macula densa receptor mechanism, senses changes in the rate of sodium chloride delivery to the distal tubule. The latter two mechanisms are influenced indirectly by renal sympathetic nerve activity which, by causing ~-adrenoceptor-mediated vasoconstriction, produces a reduction in renal blood flow and glomerular filtration rate; these alterations will produce a change in distal tubular delivery of sodium chloride. Additionally, activation of a-adrenoceptors in proximal tubular nerve terminals can increase proximal tubular sodium chloride transport with a resultant decrease in distal tubular sodium chloride delivery in the absence of changes in renal hemodynamics. Thus, the renin release response to increases in efferent RSNA can be the result of a complicated interaction of several mechanisms. In response to high level renal nerve stimulation which produces substantial changes in renal hemodynamics (50% decrease in renal blood flow) and urinary sodium excretion, Kopp et al. (1981a) have shown that the renin release is totally blocked by a combination of/3-1 and a-adrenoceptor blockade. Prostaglandin synthesis inhibitors, when given alone, produced a degree of inhibition of renin release which was similar to that produced by either/3-1 or ~-adrenoceptor blockade alone. The inhibition of renin release produced by the combination of prostaglandin synthesis inhibition and/3-1 adrenoceptor blockade was additive, whereas that produced by the combination of prostaglandin synthesis inhibition and a- adrenoceptor blockade was not greater than that produced by either intervention alone. ~-Adrenoceptor blockade abolished the renal vasoconstrictor whereas/3-1 adrenoceptor blockade and prostaglandin synthesis inhibi- 146 G.F. DiBona

tion did not affect it. Thus, high level renal nerve stimulation, which produces substantial changes in renal hemodynamics and urinary sodium excretion, results in renin release which is partly due to an activation of the /~-1 adrenoceptor mechanism. The remaining portion of the renin release is dependent on prostaglandin synthesis and derives from the a- adrenoceptor-mediated renal vasoconstriction with activation of the baroreceptor and macula densa receptor mechanisms. Using conscious sodium-depleted rats, Schiffrin et al. (1980) have reported similar results. Both indomethacin and propranolol lowered PRA, and combined administration produced an additive effect. Both intra- cerebroventricular clonidine and parenteral propranolol lowered PRA but their combined administration did not produce an additive effect. Thus, the central nervous system, through a central a-adrenoceptor pathway with peripheral mediation by #-adrenoceptors, is involved in producing the elevated PRA observed in the conscious sodium-depleted rat. Al- though a prostaglandin-dependent pathway acting in parallel to the fl- adrenoceptor was postulated, studies employing a-adrenoceptor blockade were not reported. It is possible that the heightened level of circulating catecholamines, characteristic of sodium depletion, may be contributing to the prostaglandin-dependent renin release via renal vasoconstriction (i.e., a series as opposed to a parallel pathway), as is observed with direct RNS (Kopp et al. 1981a).

~5o[ mmHg

RBF 300 f

ml/min 200t

100 L

UNaV 60f u.Eq/min 30 0 Fig. 20. Effect of suprarenal aortic constriction with and without concomitant low level renal RSR nerve stimulation (0.25 Hz) on 103ng/min renal function and renin secretion rate (RSR) in anesthetized dogs. liI See Fig. 17 for abbreviations; BA, brachial artery; FA, femoral N=101 A' ' I ' I C C R RNS RNS R artery; AC, aortic constriction. AC+ (Thames and DiBona 1979) The Functions of the Renal Nerves 147

Thames andDiBona (1979) have demonstrated that subthreshold levels of efferent RSNA can modulate the renin-release response to nonneural stimuli. A level of direct renal nerve stimulation (0.25 Hz) which, by itself, did not affect renin release, renal hemodynamics, or urinary sodium excretion, significantly augmented the renin release response to reduction in renal perfusion pressure to 50 mmHg (Fig. 20). Using different levels of direct renal nerve stimulation and renal perfusion pressure, a close interaction between the magnitudes of the two input stimuli can be shown to determine the degree to which the renin release is augmented. Using two different models of a nonfiltering kidney in which the macula densa receptor is rendered nonfunctional, the augmentation phenomenon appears to be dependent on an intact macula densa receptor mechanism (Osborn et al. 1979;Holdaas et al. 1981).

4.3.2 Prostaglandin Renal nerve stimulation at intensities producing renal hemodynamic changes increases release of prostaglandins into the renal vein in dogs (Dunham and Zirnmerman 1970; Davis and Horton 1972; Mancia et al. 1974) and in rabbits (Johns et al. 1977). Indomethacin blocked this increase in prostaglandin release (Davis and Horton 1972). The effect of RNS at lower intensities on renal prostaglandin production is not known.

4.3.3 Kallikrein As recently reviewed by Levinsky (1979) and Carretero and Scicli (1980), there is evidence that adrenergic stimulation increases renal kallikrein production. Recently our laboratory (Lawton et al., personal communica- tion) has examined the effects of graded renal nerve stimulation on urinary kaUikrein excretion (esterolytic assay). At levels of renal nerve stimulation that produced no or minimal changes in renal blood flow and glomerular filtration rate (0.5 Hz), urinary kallikrein excretion increased by 50%. At higher levels of renal nerve stimulation that produced decreases in renal blood flow and glomerular filtration rate, urinary kaUikrein excretion decreased in parallel to prestimulation levels (1.0 and 2.0 Hz) or below (4.0 Hz). Diz et al. (1980) showed that renal denervation in rats decreased PRA but not urinary PGE2 or kallikrein excretion.

4.4 Renorenal Reflexes

Responses occurring in one kidney produced by interventions on the same (ipsilateral) or the other (contralateral) kidney which are mediated by neurohumoral mechanisms are called renorenal reflexes. Previous attempts 148 G.F. DiBona

to demonstrate the existence of a renorenal reflex have employed direct electrical stimulation of afferent renal nerves or physiological stimulation of a renal receptor. Direct electrical stimulation of afferent renal nerves produced a decrease in ipsilateral efferent RNSA and in arterial pressure in rabbits (Aars and Akre 1970) and dogs (Ueda et al. 1967). In the cat, however, direct stimulation of afferent renal nerves elicits a contralateral and ipsilateral increase in efferent RSNA that is associated with an increase in arterial pressure and heart rate, no change in contralateral renal blood flow or renin release from either kidney, and mesenteric and iliac vasoconstriction (Calaresu et al. 1976, 1977). In other studies (Calaresu et al. 1978) it was demonstrated that spinal cord destruction (C,2-L-5) and administration of doses of nicotine known to block transmission at sympathetic ganglia abolished the renorenal reflex. In addition, involvement of dorsal root reflexes was excluded by demonstrating that administration of bicu- culline failed to affect the renorenal reflex. Two renorenal reflexes, corresponding to selective stimulation of renal afferent A or C fibers, were described. Francisco and DiBona (1979) have stimulated afferent renal nerves in the dog. With increasing frequency of stimulation from 1 to 16 Hz, there was a slight rise in mean arterial pressure with no change in either kidney renal blood flow but a frequency-dependent increase in femoral artery blood flow. The increases in mean arterial pressure and femoral artery blood flow were abolished by either phentolamine or guanethidine administered intravenously. Golin et al. (1980) have stimulated afferent renal nerves in the cat. There was a transient modest increase in mean arterial pressure which slowly declined to the control level. When renal perfusion pressure was held slightly below control values, afferent renal nerve stimulation produced small and equal decreases in urinary flow rate and sodium excretion, glomerular filtrtion rate, and renal blood flow in both the innervated and denervated kidney. Therefore, direct electrical stimulation of the afferent renal nerves does not produce significant alterations in renal hemodynamics of either the ipsilateral or contralateral kidney of the cat or dog. However, the situation is clearly different in the rat, since Mahoney et al. (1978) have shown that afferent renal nerve stimulation produces vasodilatation in the hindquarters and vasoconstriction in the mesenteric and renal vascular beds, with little change in arterial pressure. These responses are identical to those observed during direct electrical stimulation of the anteroventral thrid ventricle (AV3V) (Fink et al. 1978). The responses to afferent renal nerve stimulation are abolished by acute lesioning of the AV3V as well as by hexamethonium, whereas bilateral adrenalectomy has no effect (Brocly et al. 1979; Brody and Johnson 1980). Spinal cord section at T-6 abolishes the renal vasoconstriction and hindquarters vasodila- The Functions of the Renal Nerves 149 tation while preserving the mesenteric vasoconstriction. Lesions of the nucleus tractus solitarii (NTS) alternate the hindquarters vasodilatation while preserving the mesenteric and renal vasoconstriction. Thus, afferent renal nerve stimulation elicits a vascular renomesenteric reflex at the spinal level and the NTS is a component of the selective reflex arc between the kidney and the hindquarters circulation (Webb et al. 1981). Several investigators have employed physiological stimulation of renal receptors in an attempt to elicit a renorenal reflex. MacFarlane (9170), using nonquantitative morphological methods, demonstrated that renal intra-arterial injections of acetylcholine produced contralateral renal vasoconstriction that was abolished by denervation of either kidney. However, Kottra and Takacs (1980) repeated these experiments using electro- magnetic flow meter measurements of renal blood flow and measuring efferent RSNA to the contralateral kidney. Despite a substantial ipsilateral renal vasodilatation, contralateral renal blood flow was unchanged and the small increase in efferent RSNA was related to changes in mean arterial pressure. Vaughn et al. (1971) showed that the renal hemodynamic response to acute unilateral ureteral occlusion is an increase in ipsilateral renal blood flow for the first 3-6 h followed by a gradual decrease to levels below control at 12-24 h; the contralateral kidney shows an early decrease in renal blood flow followed by a gradual return to control levels. Francisco et al. (1980a) demonstrated that this contralateral renal vasoconstrictor response to ipsilateral ureteral occlusion is a renorenal reflex. The efferent limb consists of a renal mechanoreceptor which, in response to increased intrarenal pressure produced by ureteral occlusion, sends afferent signals along the ipsilateral afferent renal nerves through the spinal cord to supraspinal centers. The efferent limb consists of contralateral afferent renal sympathetic nerve fibers. In support of the involvement of supraspinal centers, spinal cord section at T-6 abolished the contralateral renal vasoconstrictor response to ipsilateral ureteral occlusion. In the spinal cat, Beacham and Kunze (1969)showed that increases in ureteral pressure still produced increases in both ipsilateral afferent and efferent renal nerve activity, suggesting that participation of supraspinal centers was not required for this reflex. They also observed a decrease in mean arterial pressure without a change in ipsilateral renal blood flow, when ureteral pressure was increased to 25-30 mmHg, whereas Francisco et al. (1980) observed an increase in mean arterial pressure and an increase in ipsilateral renal blood flow when ureteral pressure was increased to 60- 80 mmHg. These differences in hemodynamic responses suggest the possibility that different renal mechanoreceptors were activated in the two studies. Kady (1974), in both cats and dogs, showed that increases in renal vein or ureteral pressure increased afferent and decreased efferent renal 150 G.F. DiBona

nerve activity and decreased renal vascular resistance in the ipsilateral kidney; renal denervation reversed the ipsilateral renal vascular response from a vasodilatation to a vasoconstriction. Kostreva et al. (1981) have provided preliminary evidence in confirmation of Kady's results. In anesthetized vagotomized dogs, renal vein occlusion increased ipsilateral afferent renal activity and decreased contralateral efferent renal nerve activity. This decrease in contralateral efferent renal nerve activity was accompanied by a decrease in contralateral renal vascular resistance; denervation of the kidney with the renal vein occlusion eliminated both the decrease in contralateral efferent renal nerve activity and renal vascular resistance. Renal vein occlusion also inhibited cardiopulmonary sympathetic efferent nerve activity. This was associated with a decrease in right but not left ventricular contractile force; heart rate was unaffected. De- nervation of the kidney with the renal vein occlusion eliminated both the decrease in cardiopulmonary sympathetic efferent nerve activity and right ventricle contractile forces. Thus, there is good electrophysiological and functional evidence for the existence of renorenal as well as renocardiac reflexes derived from interventions which activate renal mechanoreceptors. DiBona and Rios (1980) demonstrated that, following acute renal denervation in saline-loaded rats, the ipsilateral diuresis and natriuresis are accompanied by a compensatory antidiuresis and antinatriuresis from the contralateral kidney. As reflected by direct measurements of contralateral efferent RSNA and its reversal by contralateral acute renal denervation, the compensatory contralateral renal response is mediated by the efferent renal sympathetic nerves (Fig. 21). Similar findings were subsequently reported by Colindres et al. (1980) who also showed that the anticipated

25 N=10

Left 20 Renal Nerve 15 Activity

Hz 10

5 Fig. 21. Effect of acute right renal denervation on efferent renal sympathetic oAP ::: f nerve activity to the left kidney in mmHg 80 ~ m r anesthetized rats. MAP, mean arterial Control Right Renal pressure; DNX, denervation. (DiBona DNX and Rios 1980) The Functions of the Renal Nerves 151

compensatory contralateral renal response was prevented by prior chronic renal denervation. Moss and Harrington (1980) demonstrated, in nondiuretic rats, that the ipsilateral diuresis and natriuresis which followed acute renal denervation was accompanied by a contralateral natriuresis without diuresis which was blocked by prior denervation of the kidney. These compensatory renal responses may be initiated via stimulation of the R2 renal chemoceptive receptors. Neurophysiological recording studies (Recordati et al. 1980a) have shown that ipsilateral or contralateral stimulation of both R1 and R2 renal chemoceptive receptors elicits increases in efferent RSNA which, while not altered by baroreceptor denervation, were enhanced by C-1 spinal cord section. These observations suggest that renal chemoceptive receptors and afferent renal nerve activity might influence ipsilateral and contralateral efferent RSNA through neural reflexes which are likely to be integrated at the spinal and supraspinal levels. The mechanism of the hemodynamic and renal excretory responses to acute unilateral nephrectomy have been studied. Acute unilateral nephrectomy produces an increase in mean arterial pressure, a decrease in cardiac output, and a rise in urinary cation (sodium and potassium) excretion in the absence of changes in glomerular filtration rate or renal blood flow (Humphreys and Ayus 1978; Humphreys et al. 1980). Bilateral cervical vagotomy or atropine administration abolished the cardiovascular hemodynamic changes, but the increase in urinary cation excretion was still observed (Humphreys et al. 1980). However, bilateral carotid sinus denervation abolished both the cardiovascular hemodynamic and renal excretory alterations (Ayus et al. 1978). These observations suggest that this renorenal reflex response involves the caroid sinus baroreceptors as the major afferent pathway, with efferent vagal pathways mediating the cardiovascular hemodynamic responses. The renal excretory response of the remaining kidney is not a pressure diuresis, since it occurred following bilateral cervical vagotomy and atropine administration when mean arterial pressure was unchanged; it may be related to carotid baroreceptor- mediated reflex withdrawal of efferent RSNA. Renal mechanoreceptors have been implicated in a renoadrenal reflex arc that is of importance in the maintenance of potassium homeostasis (Hiatt et al. 1981). In ureter-ligated or nephrectomized dogs infused with potassium, a nonrenal potassium homeostatic mechanism retards the development of hyperkalemia by promoting the transfer of potassium from extracellular to intracellular fluid. The potassium transfer ability in ureter- ligated dogs is less than that of equally anuric nephrectomized dogs. How- ever, the potassium transfer ability in ureter-ligated dogs can be raised to the nephrectomy level if the kidneys are denervated or by bilateral cervical vagotomy; vagotomy is without effect in ureterqigated dogs with bilateral 152 G.F. DiBona adrenalectomy or in nephrectomized dogs. Epinephrine infusion increases potassium transfer ability in anuric dogs. These studies indicate that ureteral ligation, possibly by activation of renal mechanoreceptors due to increased intrarenal pressure, initiates afferent neural impulses which course through the renal and vagus nerves and impair the potassium transfer ability by inhibiting epinephrine section from the adrenal. With renal denervation or bilateral cervical vagotomy, there is release of inhibition with resultant epinephrine secretion and restoration of potassium transfer ability to the nephrectomy level; unless the adrenals - the source of epinephrine - are removed. In the absence of neural impulses from the kidney, i.e., nephrectomized dogs, bilateral cervical vagotomy has no effect on potassium transfer ability.

4.5 HypertenNon

Several studies described a role for the renal nerves in contributing to the initiation and/or maintenance of the hypertensive state (Fink and Brody 1978; Fink and Bryan 1980). Renal denervation has been shown to delay the onset of hypertension in the spontaneously hypertensive rat (SHR) (Liard 1976; Kline et al. 1978; Winternitz et al. 1980) and the New Zea- land genetically hypertensive rat (Diz et al. 1981), to delay the onset of DOCA-salt-induced hypertension (Katholi et al. 1980a), and to lower arterial pressure in established one-kidney one-clip hypertension (Katholi et al. 1981b). In both DOCA-salt hypertensive rats, New Zealand genetically hypertensive rats and SHRs, the delay in onset of hypertension produced by renal denervation was associated with an increase in urinary sodium excretion and reduced sodium retention; the eventual development of hypertension coincided with renal reinnervation, a decrease in urinary sodium excretion, and an increased sodium retention. However, Kline et al. (1980c) noted that SHRs subjected to a second renal denervation 3 weeks after the initial operation continued to develop hypertension similar to those having only one operation and suggested that the delayed rise in arterial pressure in renal-denervated SHRs is not due to renal reinnervation. In one-kidney one-clip rats, the necessity of the renal nerves for maintenance of hypertension was independent of alterations in renin, sodium intake or excretion, water intake, or renal function. The depressor effect of renal denervation was associated with a decrease in hypothalamic norepinephrine concentration (Winternitz et al. 1981) and a decrease in peripheral sympathetic tone (Katholi et al. 1981). These data indicate that renal denervation with interruption of renal afferent fibers can modulate central nervous system sympathetic activity, leading to a decrease in peripheral sympathetic tone and arterial pressure. The Functions of the Renal Nerves 153

Kline and colleagues (1980) have shown that renal denervation prevented the increase in arterial pressure that follows cutting of the aortic depressor nerve and cervical sympathetic trunk in the rat; this effect may be mediated through changes in activity of the renin-angiotensin system (Kline and Mercer 1980b). These observations are in general agreement with studies demonstrating a generalized increase in sympathetic nervous system activity in SHRs (e.g., Judy and Farrell 1979) and DOCA-salt hypertension (reviewed in Katholi et al. 1980a). Although recordings of efferent RSNA have not been made in DOCA- salt hypertension, those that have been made in SHRs have given dis- cordant results. Judy and Farrell (reviewed in 1979), using multifiber or whole nerve recording techniques in conscious and anesthetized rats, demonstrated that basal levels of efferent RSNA were higher in SHRS than in age-matched genetic control normotensive Wistar Kyoto (WKY) rats. Thoren and Ricksten (1979), using single fiber recording techniques in anesthetized rats, showed that basal levels of efferent RSNA were 3.3 + 0.45 Hz in SHRs and 1.6 -+ 0.23 Hz in WKYs. Francisco et al. (1981), using whole nerve recording techniques in anesthetized rats, found basal levels of efferent RSNA to be similar in SHRs and WKYs. Ricksten et al. (1981), using whole nerve recording techniques in conscious unanesthetized rats, found basal levels of efferent RSNA to be slightly but not significantly greater in SHRs than in WKYs. The nerve recording studies showing no difference in basal levels of efferent RSNA between SHRs and WKYs are in agreement with the functional observations of Touw et al. (1980), who could not demonstrate any increased neural contribution to the heightened renal vascular tone in SHR as compared with WKYs. In the case of renal hypertension, Brody and colleagues (1980) have provided evidence that the afferent renal nerves, via connections to the anterior hypothalamus, may play an important role in intiating the complex alterations in blood pressure regulation that result in this form of hypertension. The area of interest in the anterior hypothalamus is the anterior portion of the ventral third cerebral ventricle (AV3V). Electrical stimulation within the AV3V and the periventricular tissue produces renal and mesenteric vasoconstriction and hindquarters vasodilation; arterial pressure decreases with AV3V stimulation, but is unchanged with periventricular trissue stimulation. The renal and mesenteric vasoconstrictor responses were abolished by ganglionic blockade with hexamethonium and surgical denervation of the organ, but were unaffected by adrenalectomy. The active hindquarters vasodilator response involves #-adrenoceptor-mediated vasodilation which is produced, in part, by release of epinephrine from nerve terminals and the adrenals (Berecek et al. 1980). Stimulation of the afferent renal nerves produced an increase in arterial pressure, renal and mesenteric vasoconstriction, and hindquarters vaso- 154 G.F. DiBona

dilation; the responses were abolished by hexamethonium, whereas bilateral adrenalectomy had no effect. The hemodynamic responses to AV3V stimulation were similar to those occurring after afferent renal nerve stimulation. Further evidence that the afferent renal nerves pro- jected to be AV3V was provided when it was shown that an acute AV3V lesion essentially abolished the arterial pressure and vascular resistance changes produced by afferent renal nerve stimulation. Thus, it appeared that renal deafferentiation might interrupt the same neural loop that is blocked by an AV3V lesion and led to the hypothesis that renal deafferentiation might block or attenuate the development of renal hypertension. In rats with single autotransplanted (i.e., denervated kidneys, the onset of hypertension in response to figure-eight wrapping of the kidney (Grollman procedure) was delayed for 8-10 weeks. These several observations indicate that the afferent renal nerves ascend to the AV3V and synapse with descending efferent pathways which are distributed to several regional vascular beds. These pathways connecting the kidney to the central nervous system may play an important role in overall cardiovascular regulation in the development of renal hypertension. The phenomenon of exaggerated natriuresis characterizes many forms of experimental hypertension. It has been described as being present (DiBona and Rios 1978) or absent (Fandewalle et a1.1978; Arendhorst and Beierwaltes 1979) in studies conducted in anesthetiezd SHRs, a finding which might be explained by the nonuniformity of renal excretory responses to isotonic saline volume expansion in SHRs obtained from different sources (Mullins and Banks 1976). On the other hand, studies in conscious animals clearly demonstrate that SHRs have an exaggerated natriuretic response to intravenous isotonic saline volume expansion (Struyker- Boudier et al. 1979, 1980; Ricksten et al. 1981). Since volume expansion decreases efferent RSNA, which in turn is capable of directly reducing renal tubular sodium reabsorption, the relationship between volume expansion, exaggerated natriuresis, and efferent RSNA was examined in SHRs. In anesthetized rats with laparotomy, Francisco et al. (1981) demonstrated that isotonic saline volume expansion produced a similar degree of inhibition of efferent RSNA in SHRs and WKYs, while the SHRs had an exaggerated natriuretic response. In light of the compound- ing influences of anesthesia and surgical stress, these studies were repeated in conscious unanesthetized SHRs. Ricksten et al. (1981) found that isotonic saline volume expansion produced a greater inhibition of efferent RSNA and an exaggerated natriuretic response in SHRs as compared with WKYs. These latter observations suggest that the greater inhibition of efferent RSNA in SHRs may contribute to the exaggerated natriuretic response by directly reducing renal tubular sodium reabsorption. These studies confirm and extend the observations of Thoren, Ricksten, and The Functions of the Renal Nerves 155 colleagues (Thoren and Ricksten 1979; Ricksten et al. 1979;Noresson et al. 1979; Thoren et al. 1979a, b; Ricksten and Thoren 1980; Ricksten 1980) which indicate that an intravenous volume load administered to SHRs is preferentially distributed centrally, resulting in a greater rise in left atrial pressure as compared with WKYs. The left atrial receptors are reset in SHRs so that a higher left atrial pressure is required for a similar degree of inhibition of efferent RSNA. Thus, volume expansion in SHRs leads to a greater rise in left atrial pressure, which is greater than that required to offset the upward resetting of left atrial receptors in SHRs, and to a greater inhibition of efferent RSNA as compared to WKYs similarly volume expanded. It is possible that this greater degree of inhibition of efferent RSNA plays an important role in the exaggerated natriuresis characteristic of this and perhaps other forms of experimental hypertension characterized by increased activity of the sympathetic nervous system (Friedman et al. 1955; Ben-Ishay et al. 1973; Takeshita et al. 1978, 1979;Fink et al. 1980). Thus, several fines of evidence indicate an increase in sympathetic neural activity in hypertension and a relationship betwen efferent RSNA, sodium retention, and the development of hypertension in different animal experimental models of hypertension which are characterized by an exaggerated natriuretic response to volume expansion. In addition, afferent renal nerves are coupled to the central nervous system as part of an integrated cardiovascular control system which may participate in the development of renal and other forms of hypertension. The importance of enhanced efferent RSNA in human essential hypertension is reflected by the work of Hollenberg et al. (1975), who showed that renal arterial infusion of phentolamine, an a-adrenoceptor antagonist, increased renal blood flow significantly in six of nine patients with mild essential hypertension but in none of 15 normal subjects.

4.6 Summary

The renal nerves serve as an important efferent control system for the reflex regulation of several renal functions. A variety of reflex mechanisms, operating singly or in concert, can produce major alterations in renal blood flow, renal tubular solute and water transport, and renal release of physiologically significant vasoactive substances. Studies in conscious unanesthetized animals demonstrate the presence of low resting levels of efferent RSNA which, even after moderate increases as observed during carotid baroreceptor reflex stimulation, do not produce renal vasoconstriction, but which, after marked increases as observed during emotion- ally stressful auditory stimuli, produce pronounced renal vasoconstriction. 156 G.F. DiBona

There is no functional evidence for sympathetic cholinergic vasodilator fibers in the kidney. Decreases or increases in efferent RSNA, produced directly or reflexly, result in parallel changes in renal tubular solute (e.g., sodium) and water reabsorption which are directly mediated by adrenergic nerve terminals containing ~-adrenoceptors in contact with renal tubular epithelial cells. Renal hemodynamic factors, peritubular physical forces, and circulating humoral substances are not involved. The proximal tubule has been identified as one site for this neural control mechanism. Efferent RSNA is a participant in the efferent limb(s) of the mechanism(s) involved in the avid renal sodium retention of certain edema-forming conditions as well as the normal physiological response to dietary sodium deprivation. This neural control mechanism is operative in the conscious unanesthetized animal. The renin release response to increases in efferent RSNA is the result of a complex interaction of several mechanisms. One part derives from stimulation of/~-1 adrenoceptors on the juxtaglomerular granular cells. The remaining portion is prostaglandin dependent and derives from ~-adrenoceptor-mediated renal vasoconstriction with activation of the baroreceptor and macula densa receptor mechanisms. Renin release in response to direct neural stimulation of the juxtaglomerular granular cells is not mediated by a-adrenoceptors. Subthreshold levels of efferent RSNA can significantly augment the renin release response to nonneural stimuli, and this appears to be dependent on an intact macula densa receptor mechanism. Renal nerve stimulation increases the renal secretion of prostaglandin and kallikrein. Renorenal reflexes can participate in physiological regulation of renal function as well as mediate the compensatory adaptive responses of renal function in the kidney contralateral to a kidney whose function has been altered. Both afferent and efferent renal nerves are involved in the control of cardiovascular and renal functions which contribute to the regulation of body fluid and electrolyte balance, arterial pressure, and the devlopment and/or maintenance of hypertension.

5 Concluding Remarks

The functions of the renal nerves are multiple. Efferent renal sympathetic nerve activity participates in the regulation of the renal circulation, as well as in the filtration, reabsorptive, and secretory processes involved in the renal handling of solutes and water and the renal release of vasoactive substances which have important roles in cardiovascular function, the regulation of arterial pressure, and the development and/or maintenance of hypertension. Afferent renal nerves participate in renorenal reflexes which mediate the compensatory adaptive functional response of the kidney The Functions of the Renal Nerves 157 contralateral to the kidney whose function has been acutely altered. In addition, via their connections to specialized centers in the brain, the afferent renal nerves are part of an integrated neurohumoral system which is involved in the regulation of body fluid and electrolyte balance, arterial pressure, and the development and/or maintenance of hypertension. In 1970, Norvell queried: "Renal nerves: are they essential?" In view of the evidence that spontaneous or induced renal denervation in man and animals impairs the ability of the kidney to adapt normally to dietary sodium restriction and leads to the development of clinically symptomatic total body sodium deficits, the answer must be an unqualified yes. While an essential role for the renal nerves can be demonstrated in this and other circumstances of modest physiological stress, further experimental work is required to define more precisely the functional role of the renal nerves in normal homeostatic regulation.

Acknowledgments. This work would not have been possible without the collaborative efforts of many colleagues. I am grateful to each of the following persons for their contributions: H. Aars, A.J. Aguflera, K. Aukland, A.D. Baines, L. Barajas, P. Bencsath, M.J. Brody, A. Fitz, B. Folkow, L.L. Francisco, K. Gorgas, C.W. Gottschalk, R. Gross, H. Holdaas, L.G. Hoversten, P. Insel, E.J. Johns, G.J. Kaloyanides, F. Kill, H. Kirch- heim, H.P. Koepchen, U. Kopp, W.J. Lawton, G. Mancia, N. Morgunov, J.L. Osborn, P.K.T. Pang, E.H. Prosnitz, G.M. Recordati, H.W. Reinhardt, S.-E. Ricksten, W. Riedel, J. Sadowski, L.L. Sawin, H. Seller, Gi.Shck, K.M. Spyer, A. Stella, L. Takacs, M.D. Thames, P. Thoren, C.S. Wilcox, T. Yao, and E.J. Zambraski. Ann Bently and Linda Hobbs provided assistance with the preparation of this manuscript. The research performed in the author's laboratory was supported by United States Public Health Service, National Institutes of Health Research Grants AM 15843, HL 14388 and HL 23898 and by research grants from the Iowa Heart Association and the Veterans Administration. Part of this review was written while the author was on leave from the University of Iowa College of Medicine and Veterans Administration Mecial Center, Iowa City, Iowa and received support from a Fogarty International Center Senior International Fellowship (FO6 TWOO363) of the National Insitutes of Health and a Veterans Administration Extended Leave for Educational Purposes. The hospitality of Professor F. Kill, Institute for Experimental Medical Research, Univer- sity of Oslo, Ullevaal Hospital, Oslo, Norway and of Docent P. Thoren and Professor B. Folkow, Institute of Physiology, University of Goteborg, Goteborg, Sweden is gratefully acknowledged.

References 1

Aars H (1972) Reflex inhibition of sympathetic nerve activity by phenoxybenzamine. Acta Physiol Scand 85:433-437 Aars H, Akre S (1968) Effect of angiotensin on sympathetic nerve activity. Acta Physiol Scand 74:134-141 Aars H, Akre S (1970) Reflex changes in sympathetic activity and arterial blood pressure evoked by afferent stimulation of the renal nerve. Acta Physiol Scand 78: 184-188 1 Literature search was concluded in June, 1981. 158 G.F. DiBona

Abe K, Sato M, Haruyama T, Sato K (1980) The role of prostaglandins in the renin release mechanism following sodium deprivation and captopril administration in humans. Proc Int Symp Prostaglandins and the Kidney. Stuttgart, West Germany, p19 Adam WR (1980) Aldosterone and dopamine receptors in the kidneys: sites for pharmacologic manipulation of renal functions. Kindey Int 18:623-635 Adrian ED, Bronk DW, Phillips G (1932) Discharges in mammalian sympathetic nerves. J Physiol 74:115-133 Alexander RW, Gill JR, Yamabe H, Lovenberg W, Keiser HR (1974) Effects of dietary sodium and of acute saline infusion on the interrelationship between dopamine excretion and adrenergic activity in man. J Clin Invest 54:194-200 Ammons WS, Santiesteban HL, Kozama S, Manning JW (1980) Carotid baroreflex regulation of plasma renin levels. Am J Physiol 239:H342-H348 Anderson RJ, Henfich WL, Erickson AL, Gross P (1980) Role of renal nerves, angiotensin II and prostaglandins in antinatriuretic response to hypercapnic acidosis. Clin Res 28:434A Andreucci VE, Dal Canto A, Corradi A, Migone L (1976a) Efferent arterioles in glomerular hemodynamics. Proc Eur Dial Transplant Assoc 12:169-173 Andreucci VE, Dal Canto A, Corradi A, Stanziate R, Migone L (1976b) Role of the efferent arteriole in glomerular hemodynamics of superficial nephrons. Kidney Int 9:475-480 Arendhorst WJ, B eierwaltes WH (1979) Renal tubular reabsorption in spontaneously hypertensive rats. Am J Physiol 237 :F38-F47 Arruda JAL, Sabatini S (1980) Dopamine inhibits water transport in the toad bladder: role of locally formed dopamine. Clin Res 28:782A Astrom A, Crafford J (1967) Afferent activity recorded in the kidney nerves of rats. Acta Physiol Scand 70:10-15 Astrom A, Crafford J (1968) Afferent and efferent activity in the renal nerves of cats. Acta Physiol Scand 74:69-78 Atlas D, Melamed E, Lahar M (1977) Beta adrenergic receptors in rat kidney. Lab Invest 36:465-468 Aukland K (1976) Renal blood flow. In: Thurau K (ed) International review of phyiol- ogy: Kidney and urinary tract physiology II, Vol 2. University Park, Baltimore, pp 25-79 Aukland K (1980a) "Redistribution" of intrarenal blood flow: facts or methodological artifacts. In: Leaf A, Giebisch G (eds) Renal pathophysiology - recent advances. Raven, New York, pp 145-154 Aukland K (1980b) Methods for measuring renal blood flow: total flow and regional distribution. Annu Rev Physiol 42:543-555 Ayus JC, Stanton C J, Eneas JF, Humphreys MH (!978) Mechanisms involved in the reflex circulatory changes initiated by acute unilateral nephrectomy. Proc Int Congr Nephrol 7 :F-7 Azer M, Gannon R, Kaloyanides GJ (1972) Effect of renal denervation on the antinatriuresis of caval constriction. Am J Physiol 222:611-616 Baines AD, Chan W (1980) Production of urine free dopamine from DOPA; a micropuncture study. LifeSci 26:253-259 Baines A, Morgunov N (1980) Catecholamines and sodium excretion. In: Lichardus B, Schrier RW, Ponec J (eds) Hormonal regulation of sodium excretion. Elsevier/ North Holland, Amsterdam, pp 21-32 Baines AD, Craan A, Chan W, Morgunov N (1979) Tubular secretion and metabolism of dopamine, norepinephrine, methoxytyramine and normetanephrine by the rat kidney. J Pharmacol Exp Ther 208:144-147 Barajas L (1978) Innervation of the renal cortex. Fed Proc 37:1192-1201 Barajas L (1979) Anatomy of the juxtaglomerular apparatus. Am J Physiol 237 :F333 -F343 The Functions of the Renal Nerves 159

Barajas L (1981 ) The juxtaglomerular apparatus: anatomical considerations in feedback control of glomerular filtration rate. Fed Proc 40:78-86 Barajas L, Wang P (1975) Demonstration of acetylcholinesterase in the adrenergic nerves of the renal glomerular arterioles. J Ultrastruct Res 53:244-253 Barajas L, Wang P (1978) Myelinated nerves of the rat kidney. J Ultrastruct Res 65: 148-162 Barajas L, Wang P (1979) Localization of tritiated norepinephrine in the renal arteriolar nerves. Anat Res 195:525-534 Barajas L, Silverman A J, Muller J (1974) Ultrastructural localization of acetylcholinesterase in the renal nerves. J Ultrastruct Res 49:297-311 Barajas L, Wang P, Desantis S (1976) Light and electron microscopic localization of acetylcholinesterase activity in the rat renal nerves. Am J Anat 147:219-234 Barger AC, Liebowtiz MR, Muldowney FP (1959a) The role of the kidney in the homeostatic adjustments of congestive heart failure. J Chronic Dis 9:571-582 Barger AC, Muldowney FP, Liebowitz MR (1959b) Role of the kidney in the pathogenesis of congestive heart failure. Circulation 20:273-285 Baum T, Shropshire AT (1973) Reduction of sympathetic outflow by central administration of L-dopa, dopamine and norepinephrine. Neuropharmacology 12:49-56 Baum T, Shropshire AT (1975) Inhibition of efferent sympathetic nerve activity by 5-hydroxytryptoplian in centrally administered 5-hydroxytryptamine. Neuro- pharmacology 14:227-233 Beacham WS, Kunze DL (1969) Renal receptors evoking a spinal vasomotor reflex. J Physiol 201:73-85 Beierwaltes WH, Schryver S, Olson PS, Romerao JC (1980) Interaction of the prostaglandin and renin-angiotensin systems in isolated rat glomeruli. Am J Physiol 239: F602-F608 Bell C, Lang WJ (1973) Neural dopaminergic vasodilator control in the kidney. Nature 246:27-29 Bell C, Lang WJ, Laska F (1978) Dopamine-contalning vasomotor nerves in the dog kidney. J Neurochem 31:77-83 Benchetrit G, Eteradossi J, Lemarchands H (1966) Effects d'une enervation chronique du rein sur la diurese et la saliurese du chien eveille. Pathol Biol (Paris) 14:944-951 Bello-Reuss E (1980) Effect of catecholamines on fluid reabsorption by the isolated proximal convoluted tubule. Am J Physiol 238:F347-F352 Bello-Reuss E, Colindres RE, Pastoriza-Munoz E, Mueller RA, Gottschalk CW (1975) Effects of acute unilateral denervation in the rat. J Clin Invest 56:208-217 Bello-Reuss E, Trevino DL, Gottschalk CW (1976) Effect of renal sympathetic nerve stimulation on proximal water and sodium reabsorption. J Clin Invest 57:1104- 1107 Bello-Reuss E, Pastoriza-Munoz E, Colindres RE (1977) Acute unilateral renal denervation in rats with extracellular volume expansion. Am J Physiol 232:F26-F32 Bencsath P, Szalay L, Demeczky L, Takacs L (1971) Effects of chlorothiazide and furosemide on sodium and water excretion after unilateral splanchicotomy in the dog. Nephron 8:329-343 Bencsath P, Bonvalet J-P, De Rouffignac C (1972) Tubular factors in denervation diuresis and natriuresis. In: Worz H, Spinelli F (eds) Recent advances in renal physiology. Karger, Basel, pp 96-106 Bencsath P, Asztalos B, Szalay L, Takacs L (1979) Renal handling of sodium after chronic renal sympathectomy in the anesthetized rat. Am J Physiol 236:F513- F518 Ben-Ishay D, Knudsen KD, Dahl LK (1973) Exaggerated response to isotonic saline loading in genetically hypertension-prone rats. J Lab Clin Med 82:597-604 Bennett ED, Keddie J (1974) Increased glomerular filtration in patients with myocardial infarction. Clin Sci 47:8-9 160 G.F. DiBona

Bennett ED, Brooks NH, Kedd' 1, Lis Y, Wilson A (1977) Increased renal function in patients with acute left ventricular failure: a possible homeostatic mechanism. Clin Sci 52:43-50 Bennett ED, Brooks NH, Lis Y, Wilson A (1979) Is the elevated renal function in patients with acute heart failure a homeostatic mechanism? In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge Univ, Cambridge, p 468 Berecek KH, Shaffer RA, Brody MJ (1980) Circulating epinephrine is the source for the sympathetic transmitter mediating active beta-adrenergic vasodilation. Circula- tion (Suppl III) 62:111-24 Berl T, Henrich WL, Erickson AL, Schrier RW (1979) Prostaglandins in the beta adrenergic and baroreceptor mediated secretion of renin. Am J Physiol 236:F472-F477 Bernard C (1859) Lecons sur les proprietes physiologiques des liquides de l'organisme. Bailliere, Paris, pp 172-173 Berne RM (1952) Hemodynamics and sodium excretion of denervated kidney in anesthetized and unanesthetized dog. Am J Physiol 171:148-158 Berthelsen S, Pettinger WA (1977) A functional basis for classification of alpha adrenergic receptors. Life Sci 21:595-606 Besarab A, Silva P, Landsberg L, Epstein FH (1977) Effect of catecholamines on tubular function in the isolated perfused rat kidney. Am J Physiol 233:F39-F45 Better OS, Massry SG (1978) Effect of chronic bile duct obstruction on renal handling of salt and water. J Clin Invest 51:402-411 Bevan JA (1978) Vascular neuroeffector mechanisms. Raven, New York Blackshear JL, Spielman WS, Knox FG, Romero JC (1979) Dissociation of renin release and renal vasodilatation by prostaglandin synthesis inhibitors. Am J Physiol 237: F20-F24 Blair ML (1980) Renin secretion rate is increased by infusion of alpha adrenoceptor agonists into the renal artery. Fed Proc 39:1084 Blair ML (1981) Inhibition of renin secretion by intrarenal alpha adrenoceptor blockade. Am J Physio1240:E682-E688 Blake WD (1962) Relative roles of glomerular filtration and tubular reabsorption in denervation diuresis. Am J Physiol 202:777-780 Blantz RC (1980) Segmental renal vascular resistance: single nephron. Annu Rev Physiol 42:573-588 Blantz RC, Konnen KS, Tucker BJ (1976) Angiotensin II effects upon the glomerular microcirculation and ultrafiltration coefficient of the rat. J Clin Invest 57:419-434 Blasingham MC, Shade RE, Share L, Nasjletti A (1980) The effect of meclofenamate on renal bood flow in the unanesthetized dog: relation to renal prostaglandins and sodium balance. J Pharmacol Exp Ther 214:1-4 Blaufox MD, Lewis EJ, Jagger P, Lauler D, Hickler R, Merrill JP (1969a) Physiologic respones of the transplanted human kdiney. N Engl J Med 280:62-66 Blaufox MD, Lewis EJ, Jagger P, Lauler D, Hickler R, Merrill JP (1969b) Perseverance of the renal nerves. N Engl J Med 280:448-449 Blendis LM, Auld RB, Alexander EA, Levinsky NG (1972) Effect of renal beta and alpha adrenergic stimulation on proximal sodium reabsorption in dogs. Clin Sci 43: 569-576 Block MA, Wakim KG, Mann FC (1952a) Circulation through kidney during stimulation of the renal nerves. Am J Physiol 169:659-669 Block MA, Wakim KG, Mann FC (1952b) Renal function during stimulation of renal nerves. Am J Physiol 169:670-677 Bond GC, Lightfoot B (1981) Role of renal nerves in mediating changes in renin secretion during CPPV. Fed Proc 40:558 Bonjour J-P, Churchill PC, Malvin RL (1969) Change of tubular reabsorption of sodium and water after renal denervation in the dog. J Physiol 204:571-582 Boykin J, Cadnapaphomchal P, Burke T, McDonald KM, Schrier RW (1974) Mecha- nism of the diuretic effect of atrial tachycardia. Clin Res 22:265A The Functions of the Renal Nerves 161

Bricker NS, Staffon RA, Mahoney EP, Merrill JP (1958) The functional capacity of the kidney denervated by autotransplantation in the dog. J Clin Invest 37:185-193 Brod J, Fejfar Z, Fajfarova MH (1954) The role of neuro-humoral factors in the genesis of renal hemodynamic changes in heart failure. Acta Med Scand 148:273- 290 Brody M (1962) Mechanisms of renal vasodilatation. Fed Proc 21:111 Brody MJ, Johnson AK (1980) Role of the anteroventral third ventricle region in fluid and electrolyte balance, arterial pressure regulation and hypertension. In: Martini L, Ganong WF (eds) Frontiers in neuroendocrinology, vol 6. Raven, New York, pp 249-292 Brody MJ, Fink GD, Buggy J, Haywood JR, Gordon FJ, Knuepfer M, Mow M, Mahoney L, Johnson AK (1979) Critical role of the anteroventral third ventricle (AV3V) region in development and maintenance of experimental hypertension. In: Meyer P, Schmitt H (eds) Nervous system and hypertension. Flammarion, Paris, pp 76-84 Brosnihan KG, Szilagyi JE, Masaki Z, Ferrario CM (1978) Interaction of sodium and catecholamines on control of blood pressure. Physiologist 21:13 Brown AM (1980) Receptors under pressure. An update on baroreceptors. Circ Res 46:1-10 Burn JH, Rand MJ (1965) Acetylcholine in adrenergic transmission. Annu Rev Phar- macol 5 : 163-182 Cacciaguida RJ, Pablo NC, Basilio RD, Porush JG (1969) Antinatriuresis associated with propranolol administration in the dog. Nephron 11:58-64 Calaresu FR, Stella A, Zanchetti A (I 976) Hemodynamic responses and renin release during stimulation of afferent renal nerves in the cat. J Physiol 255:687-700 Calaresu FR, Stella A, Zanchetti A (1977) The role of efferent and afferent renal nerves in the release of renin in the cat. In: Buckley JP, Ferrario CM (eds) Central actions of angiotensin and related hormones. Pergamon, New York, pp 113-122 Calaresu FR, Kim P, Nakamura H, Sato A (1978) Electrophysiological characteristics of renorenal reflexes in the cat. J Physiol 283:141-154 Campbell WB, Zimmer JA (1980) Insulin-induced renin release: blockade by indomethacin in the rat. Ctin Sci 58:415-428 Campbell WB, Graham RM, Jackson EK (1979) Role of renal prostaglandins in sympathetically mediated renin release in the rat. J Clin Invest 64:448-456 Cant JR, Vander AJ (1973) Sodium excretion and intrarenal distribution of blood flow with small doses of norepinephrine. Fed Proc 32:353 Carlson DE, Schramm LP (1978) Humoral and mechanical factors modulating neural input to the renal vasculature. Am J Physiol 235 :R64-R75 Carlsson E, Ablad B, Brandstrom A, Carlsson B (1972) Differentiated blockade of the chronotropic effects of various adrenergic stimuli in the cat heart. Life Sci 1 I: 953-958 Carrara MC, Baines AD (1976) Propranolol induces acute natriuresis by beta blockade and dopaminergic stimulation. Can J Physiol Pharmacol 54:683-691 Carriere S, Cardinal J, Le Grimmellec CL (1980) Influence of sodium intake on catecholamine release by angiotensin and renal nerve stimulation in dogs. Can J Physiol Pharmacol 58:1092-1101 Caretero OA, Scicli AG (1980) The renal kallikrein-kinin system. Am J Physiol 238: F247-F255 Chaimovitz C, Massry SG, Friedler RM, Coburn JW (1974) Effect of renal denervation and alpha adrenergic blockade on sodium excretion in dogs with chronic ligation of the common bile duct. Proc Soc Exp Biol Med 146:764-770 Chan YL (1980a) The role of norepinephrine in the regulation of fluid absorption in the rat proximal tubule. J Pharmacol Exp Ther 215:65-70 Chan YL (1980b) Adrenergic control of bicarbonate absorption in the proximal con- vouted tubule of the rat kidney. Pfluegers Arch 388:159-164 162 G.F. DiBona

Chapman LW, Mittman U, Meehan JP (1971) Neural effect of cardiac receptors on renal salt excretion. Fed Proc 30:608 Ciriello J, Calaresu FR (1980) Hypothalamic projections of renal afferent nerves in the cat. Can J Physiol Pharmacol 58:574-576 Clement DL, Pelletier CL, Shepherd JT (1972) Role of vagal afferents in the control of renal sympathetic nerves in the rabbit. Circ Res 31:824-830 Click RL, Joyner WL, Gilmore JP (1979) Reactivity of glomerular afferent and efferent arterioles in renal hypertension. Kidney Int 15:109-115 Coleridge HM, Coleridge JCG (1980) Cardiovascular afferents involved in regulation of peripheral vessels. Annu Rev Physiol 42:413-427 Colindres RE, Spielman WS, Moss NG, Harrington WW, Gottschalk CW (1980) Func- tional evidence for renorenal reflexes in the rat. Am J Physiol 239:F265-F270 Concha J, Norris B (1968) Studies on renal vasomotion. Br J Pharmacol 34:277-290 Coote JH, MacLeod VH (1974) The influence of bulbospinal monoaminergic pathway on sympathetic nerve activity. J Physiol 241:453-475 Cornish KG, Gilmore JP (1981) Failure of increased left atrial pressure to alter renal function in the conscious non-human primate. Fed Proc 40:588 Dampney RAL, Stella A, Golin R, Zanchetti A (1979) Vagal and sinoaortic reflexes in postural control of circulation and renin release. Am J Physio1237 :H 146-H 152 Data JL, Gerber JG, Crump WL, Frohlich JC, Hollifield JW, Nies AS (1978) The prostaglandin system. A role in canine baroreceptor control of renin release. Circ Res 42:454-458 Davila D, Davila T, Oliw E, Anggard E (1978) The influence of dietary sodium on urinary prostglandin excretion. Acta Physiol Scand 103:100-106 Davis HA, Horton EW (1972) Output of prostaglandins from the kidney, its increase on renal nerve stimulation and its inhibition by indomethacin. Br J Pharmacol 46: 658-675 Davis JO, Freeman RH (1976) Mechanisms regulating renin release. Physiol Rev 56: 1-56 De Chatel R (1978) Mechanism of carotid occlusion diuresis. Acta Physiol Acad Sci Hung 52:367-374 De Forrest JM, Davis JO, Freeman RH, Seymour AA, Row BP, Williams GM, Davis TP (1980) Effects of indomethacin and meclofenamate on renin release and renal hemodynamic function furing chronic sodium depletion in conscious dogs. Circ Res 47:99-107 De Haven J, Sherwin R, Hendler R, Felig P (1980) Nitrogen and sodium balance and sympathetic nervous system activity in obese subjects treated with a low calorie protein or mixed diet. N Engl J Med 302:477-483 De Muylder GG (1952) The "neurility" of the kidney. Blackwell, Oxford De Torrente A, Robertson GL, McDonald KM, Schrier RW (1975) Mechanism of diuretic response to increased left atrial pressure in the anesthetized dog. Kidney Int 8:355-361 DiBona GF (1977) Neurogenic regulation of renal tubular sodium reabsorption. Am J Physio1233 :F73-F81 DiBona GF (1978) Symposium: neural control of renal function. Fed Proc 37:1191- 1221 DiBona GF (1981) The role of the renal sympathetic nerves in the control of renal function. In: Worcel M, Bonvalet JP, Langer SZ, Menard J, Sassard J (eds) New trends in arterial hypertension. INSERM Symposium No 17. Elsevier/North Hol- land, Amsterdam, pp 225-240 DiBona GF, Johns EJ (1980) A study of the role of renal nerves in the renal responses to 60 ° head-up tilt in the anesthetized dog. J Physiol 299:117-126 DiBona GF, Osborn JL (1981) Nature of renal tubular adrenoceptor medaiting neural regulation of sodium reabsorption. Fed Proc 40:553 The Functions of the Renal Nerves 163

DiBona GF, Rios LL (1978) Mechanism of exaggerated diuresis in spontaneously hypertensive rats. Am J Physiol 235 :F409-F416 DiBona GF, Rios LL (1980) Renal nerves in compensatory renal responses to contralateral renal denervafion. Am J Physiol 238 :F26-F30 DiBona GF, Sawin LL (1981) Renal innervation required for renal adaptation to low sodium diet. Clin Res 29:553A DiBona GF, Zambraski E J, Aguilera A J, Kaloyanides GJ (1977) Neurogenic control of renal tubular sodium reabsorption in the dog. Circ Res (Supp I) 40:I-127-1-130 DiBona GF, Johns EJ, Osborn JL (1981) The effect of vagotomy on 60 ° head-up tilt. J Physiol 320:293-302 Dinerstein RJ, Vannice J, Henderson RC, Roth LJ, Goldberg LI, Hoffmann PC (1979) Histofluorescence techniques provide evidence for dopamine-containing neuronal elements in canine kidney. Science 205:497 -499 DiSalvo J, Fell C (1971) Changes in renal blood flow during renal nerve stimulation. Proc Soc Exp Biol Med 136:150-153 Diz DI, Baer PG, Nasjletti A (1980) Influence of renal nerves on intrarenal hormonal systems. Fed Proc 39:1084 Diz DI, Nasjletti A, Baer PG (1981) Effect of renal denervation on development of hypertension, plasma renin and urinary excretion of kallikrein, PGE2 and sodium in the New Zealand genetically hypertensive rat. Fed Proc 40:435 Donald DE (1979) Studies on the release of renin by direct and reflex activation of renal sympathetic nerves. Physiologist 22:39-42 Donald DE, Shepherd JT (1978) Reflexes from the heart and lungs: physiological curiosities or important regulatory mechanisms. Cardiovasc Res 12:449-469 Donald DE, Shepherd JT (1980) Autonomic regulation of the peripheral circulation. Annu Rev Physiol 42:429-439 Dunham EW, Zimmerman BG (1970) Release of prostaglandin-like material from dog kidney during nerve stimulation. Am J Physiol 219:1279-1285 Dunn MJ, Liard JF, Dray F (1978) Basal and stimulated rates of renal secretion and excretion of prostaglandins E2, F2 and 13,14-dihydrol5-keto F 2 in the dog~ Kidney Int 13:136-143 Echtenkamp SF, Gilmore JP (1980) Intravascular mechanoreceptor modulation of renal sympathetic nerve activity in the cat. Am J Physiol 238:H801-H808 Echtenkamp SF, Zucker IH, Gilmore JP (1980) Characterization of high and low pressure baroreceptor influences on renal nerve activity in Macaca fascicularis. Circ Res 46:726-730 Effendigil MC, Harley A, Deegan T, McKendrick CS (1975) Changes in GFR following myocardial infarction. Cardiovasc Res 9:741 Ehrhart IC, Bond GC, Ginsburg JM (1979) Indomethacin increases renal vascular resistance after adrenergic interruption in the dog. Proc Soc Exp Biol Med 162: 112-115 Eliahou HE, Gavendo S, Serban I, Kapuler S, Iaina A (1980) Beta adrenergic receptors in rat kidneys. Proc Int Syrup Radionuclides Nephrol Thieme, Stuttgart. 4:106-110 Engelhorn R (1957) Aktionspotentiale der Nierennerven. Arch Exp Pathol Pharmakol 231:219-234 Epstein M (1978) Renal effects of head-out water immersion in man: implications for an understanding of volume homeostasis. Physiol Rev 58: 529-581 Epstein SE, Braumwald E (1966) The effect of beta adrenergic blockade on patterns of urinary sodium excretion. Ann Int Med 65:20-27 Epstein M, Lifschitz MD (1980) Volume status as a determinant of the influence of renal PGE on renal function. Nephron 25 : 157-159 Fater DC, Sundet WD, Schultz HD, Goetz KL (1980) Cardiac denervation eliminates the diuretic response elicited by increasing left atrial pressure with a balloon. Fed Proc 39:951 164 G.F. DiBona

Fedina L, Katunskii AY, Khayutin VM, Mitsanyi A (1966) Responses of renal sympathetic nerves to stimulation of afferent A and C fibers of tibial and mesenterial nerves. Acta Physiol Acad Sci Hung 29:157-176 Fedina L, Kovach GB, Huszar V (1970) Effect of 1-(4-oxyphenyl)-2Nbutylamino- ethanone hydrochlorine (BON) on blood circulation. 3. Effect on the sympathetic nerve fibers of the heart and kidneys. Arzneim Forsch 20:1656-1659 Felder R, Pelyao J, Wargo A, Schoelkopf L, Cooke M, Jose P, Eisner G (1980a) Glo- merular adrenergic receptors. Physiologist 23:162 Felder R, Schoekopf L, Pelazo J, Blecher M, Calcagno P, Eisner G, Jose P (1980b) Adrenergic and dopaminergic receptors in glomeruli and cortical tubules. Proc Am Soc Nephrol 13:132A Felder R, Pelayo J, Blecher M, Calcagno P, Eisner G, Jose P (1981) Multiple renal dopamine receptors. Clin Res 29:462A Felder RB, Thames MD (1980) Reflex depressor responses to epicardial bradykinin mediated by cardiac sympathetic afferents. Circ (Supp III) 62:III-135 Ferrario CM, McCubbin JW, Berti G (1976) Centrally mediated hemodynamic effects of angiotcnsin. In: Onesti G, Fernandez M, Kim KE (eds) Regulation of blood pressure by the central nervous system. Grune and Stratton, New York, pp 175-182 Fewell JE, Bond GC (1979) Renal denervation eliminates the renal response to continuous positive-pressure ventilation. Proc Soc Exp Biol Med 161:574-578 Fink GD, Brody MJ (1978) Neurogenic control of the renal circulation in hyperten- son. Fed Proc 37:1202-1208 Fink GD, Bryan WJ (1980) Renal vascular resistance and reactivity in the neurogenic hypertensive rat. Am J Physio1239:F474-F477 Fink GD, Buggy J, Haywood JR, Johnson AK, Brody MJ (1978) Hemodynamic effects of electrical stimulation of forebrain angiotensin and osmosensitive sites. Am J Physio1235 :H445-H451 Fink GD, Takeshita A, Mark AL, Brody MJ (1980) Determinants of renal vascular resistance in the Dahl strain of genetically hypertensive rat. Hypertension. 2: 274-280 Fisher SJ, Mslvin RL (1980) Role of neural pathways in renin response to intravascular volume expansion. Am J Physio1238 :H611 -H617 Folkow B, Johannson B, Lofving B (1961) Aspects of functional differentiation of the sympatho-adrenergic control of the cardiovascular system. Med Exp 4:321-328 Francisco LL, DiBona GF (1979) Hemodynamic effects of afferent renal nerve stimulation. Fed Proc 37:1312 Francisco LL, Hoversten LG, DiBona GF (1980a) Renal nerves in the compensatory adaptation to ureteral occlusion. Am J Physio1238 :F229-F234 Francisco LL, Osborn JL, DiBona GF (1980b) The role of prostaglandins in macula densa mediated renin release in the rat. Fed Proc 39:826 Francisco LL, Sawin LL, DiBona GF (1981) Renal sympathetic nerve activity and the exaggerated natriuresis of the spontaneously hypertensive rat. Hypertension 3: 134-138 Fray JCS (1980) Stimulus-secretion coupling of renin. Circ Res 47:485-493 F-ray JCS, Johnson MD, Barger AC (1977) Renin release and pressor response to renal arterial hypotension: effect of dietary sodium. Am J Physiol 233 :H 191 -H 195 Friedman SM, Hinke JAM, Hardwick DF (1955) Sodium tolerance in experimental hypertension. Circ Res 3:297-302 Friggi A, Chevalier-Cholat A-M, Bodard H (1977a) Effects of a beta-adrenergic blocking drug atenolol, on efferent renal nerve activity in rabbits. Experientia 33:1207- 1208 Friggi A, Chevalier-Cholat A-M, Torresani J (1977b) Reduction of efferent renal nerve activity by propranolol in rabbits. Acad Sci Comptes Rendus 284:1835-1837 Frolich JC, Hollifield JW, Wilson JP, Sweetman BJ, Seyberth HW, Oates JA (1976) Suppression of plasma renin activity in man: independence of sodium retention. Clin Res 24:271 The Functions of the Renal Nerves 165

Fukiyama K (1972) Central action of angiotensin and hypertension-increased central vasomotor outflow by angiotensin. Jpn Circ J 36:599-602 Gallardo R, Pang PKT, Sawyer WH (1980) Neural influences on bullfrog renal functions. Proc Soc Exp Biol Med 165:233-240 Gauer OH, Henry JP (1976) Neurohormonal control of plasma volume. In: Guyton AC, Cowley AW (eds) International review of physiology: cardiovasculr physiology II, vol 9. University Park, Baltimore, pp 145-190 Gavendo S, Kapuler S, Serban I, Iania I, Ben-David E, Eliahou H (1980) Beta-1 adrenergic receptors in kidney tubular cell membrane in the rat. Kidney Int 17:764-770 Gazdar A (1969) Perseverance of renal nerves. N Engl J Med 280:448-449 Gazdar AF, Dammin GF (1970) Neural degeneration and regeneration in human renal transplants. N Engl J Med 283:222-224 Gebber GL (1980) Central oscillators responsible for sympathetic nerve discharge. Am J Physiol 239:H143-H155 Gerber JG, Keller RT, Nies AS (1979) Prostaglandins and renin release: the effect of PGI2, PGE2 and 13,14 dihydroxy PGE2 on the baroreceptor mechanism of renin release in the dog. Circ Res 44:796-799 Gerber JG, Olson RD, Nies AS (1980) The importance of the adrenals in the sympathetic mediated increase in plasma renin activity during hypothensive hemorrhage. Circ (Supp III) 62:111-222 Gill JR Jr (1969) The role of sympathetic nervous system in the regulation of sodium excretion by the kidney. In: Ganong WF, Martin L (eds) Frontiers in neuroendocrinology. Oxford Univ, London Toronto, pp 289-305 Gill JR Jr (1979) Neural control of renal tubular sodium reabsorption. Nephron 23: 116-118 Gill JR Jr, Bartter FC (1966) Adrenergic nervous system in sodium metabolism. II. Effects of guanethidine on the renal response to sodium deprivation in normal man. N EnglJ Med 275:1466-1471 Gill JR Jr, Casper AGT (1969) Role of the sympathetic nervous system in the renal response to hemorrhage. J Clin Invest 48:915-922 Gill JR Jr, Casper AGT (1971) Depression of proximal tubular sodium reabsorption in the dog in response to renal beta adrenergic stimulation by isoproterenol. J Clin Invest 50:112-118 Gill JR Jr, Casper AGT (1972) Effect of renal alpha adrenergic stimulation on proximal tubular sodium reabsorption. Am J Physio1233:1201 - 1205 Fill JR Jr, Carr AA, Fleischmann LE, Casper AGT, Bartter, FC (1967) Effects of pentolinium on sodium excretion in dogs with constriction of the vena cava. Am J Physiol 212:191-196 Gilmore JP (1964) Contribution of baroreceptors to the control of renal function. Circ Res 14:301-317 Gilmore JP, Cornish KG, Rogers SD, Joyner WL (1980) Direct evidence for myogenic autoregulation of the renal microcirculation in the hamster~ Circ Res 47:226-230 Gilmore JP, Zucker IH (1975) The contribution of atrial stretch receptors to salt and water homeostasis in the human. Basic Res Cardiol 70:355-363 Gilmore JP, Zucker IH (1978) Failure of left atrial distention to alter renal function in the nonhuman primate. Circ Res 42:267-270 Goetz KL (1979) A search for evidence linking atrial receptors to renal regulatory mechanism.s In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge Univ, Cambridge, pp 213-233 Goetz KL, Bond GC (1973) Reflex diuresis during tachycardia in the dog. Circ Res 32:434-441 Goetz KL, Bond GC, Bloxham DD (1975) Atrial receptors and renal function. Physiol Rev 55 : 157:205 Goetz KL, Wang BC, Hakumaki MOK, Fater DC, Geer PG, Sunder WD (1981) Cardio- vascular, renal and humoral effects of applying local anesthetic to the atria of conscious dogs. Proc Soc Exp Biol Med 167:101-109 166 G.F. DiBona

Goldberg LI (1979) The dopamine vascular receptor. In: Imbs JL, Schwartz J (eds) Peripheral dopaminergic receptors: Proceedings of the satellite symposium of the 7th International Congress of Pharmacology. Pergamon, New York, pp 408 Goldberg LI, Kohli JD (1979) Peripheral pre- and post-synaptic dopamine receptors: are they different from dopamine receptors in the central nervous system? Commun Psychopharmacol 3:447-456 Goldberg LI, Weder AB (1980) Connections between endogenous dopamine, dopamine receptors and sodium excretion: evidences and hypotheses. Rec Adv Clin Pharmacol 3:149-166 Goldberg LI, Volkman PH, Kohli JD (1978) A comparison of the vascular dopamine receptor with other dopamine receptors. Annu Rev Pharmacol Toxicol 18:57-79 Golin R, Busnardo I, Stella A, Zanchetti A (1980) Effects of afferent renal stimulation on renal functions and hemodynamics. Eur J Clin Invest 10:14 Gomer SK, Zimmerman BG ( 1972) Determination of sympathetic vasodilator responses during renal nerve stimulation. J Pharmacol Exp Ther 181:75-82 Gomez DM (1951) Evaluation of renal resistances with specific reference to changes in essential hypertension. J Clin Invest 30:1143-1155 Gordon D, Peart WS, Wilcox C S (1979) Requirement of the adrenergic nervous system for conservation of sodium by the rabbit kidney. J Physiol 293:24P Gorgas K (1978a) Innervation of the juxtaglomerutar apparatus. In: Coupland RE, Forssman WG (eds) Peripheral neuroendocrine interaction. Springer, Berlin Heidel- berg New York, pp 144-152 Gorgas K (1978b) Struktur und Innervation des juxtaglomerularen Apparates der Ratte. Adv Anat 54:1-84 Gottschalk CW (1978) Symposium: Control of kidney function by the nervous system. Proc Int Cong Nephrol 8:544-571 Gottschalk CW (1979) Renal nerves and sodium excretion. Annu Rev Physiol 41: 229-240 Graham RM, Brabson JH, Stephenson WH, Pettinger WA (1978) Increased renal alpha adrenergic receptors in genetically hypertensive rats. Clin Res 26: 363A Graham RM, Sagalowsky AI, Pettinger WA, Murphy T, Gandler T, Sanford SE (1980) Renal alpha receptors in experimental hypertension in the rat. Fed Proc 39:497 Grandjean B, Annat G, Vincent M, Sassard J (1978) Influence of renal nerves on renin secretion in the conscious dog. Pfluegers Arch 373:161-165 Greven J, Klein H (1977) Effects of dopamine on whole kidney function and proximal transtubular volume fluxes in the rat. Naunyn Schmiedebergs Arch Pharmacol 296: 289-292 Grignolo A, Koepke JP, Obrist PA (1980) Urine and sodium output and glomerular filtration rate during treadmill exercise and shock-avoidance in saline-infused dogs. Physiologist 23 : 105 Gross R, Kirchheim H (1980) Effects of bilateral carotid occlusion and auditory stimulation on renal blood flow and sympathetic nerve activity in the conscious dog. Pfluegers Arch 383:233-239 Gross R, Ruffman K, Kirchheim H (1979 The separate and combined influences of common carotid occlusion and nonhypotensive hemorrhage on kidney blood flow. Pfluegers Arch 379:81-88 Gross R, Kirchheim H, Ruffmann K (1981 a) Effect of carotid occlusion and of p erfu- sion pressure on renal function in conscious dogs. Circ Res 48:774-784 Gross R, Hackenburg H-M, Hackenthal E, Kirchheim H (198 lb) Interaction between perfusion pressure and sympathetic nerves in renin release by carotid baroreflex in conscious dogs. J Physiol 313:237-250 Grossman RA, Rosing DR, Szidon JP, Goldberg M (1974) The polyuria of paroxysmal tachycardia: mode and mechanism. Clin Res 221:572A Hall JE, Guyton AD, Cowley AW (1977a) Dissociation of renal blood flow and filtration rate autoregulation by renin depletion. Am J Physiol 232:F215-F221 The Functions of the Renal Nerves 167

Hall JE, Guyton AC, Jackson TE, Coleman TG, Lohmeier TE, Trippodo NC (197b) Control of glomerular filtration rate by renin-angiotensin system. Am J Physiol 233:F366-F372 Heinbecker P, White HL (1941) Hypothalamicohypophysealsystem and its relationship to water balance in the dog. Am J Physiol 133:582-593 Henrich WL, Anderson RJ, Berns AS, McDonald KM, Paulsen PJ, Berl T, Schrier RW (1978) The role of renal nerves and prostaglandins in control of renal hemodynamics and plasma renin activity during hypotensive hemorrhage in the dog. J Clin Invest 61:744-750 Henrich WL, Schfier RW, Bed T (1979) Mechanisms of renin secretion during hemorrhage in the dog. J Clin Invest 64:1-7 Hermansson K, Larson M, Kallskog O, Wolgast M (1981) Influence of renal nerve activity on arteriolar resistance, ultrafiltration dynamics and fluid reabsorption. Pfluegers Arch 389:85-90 Hiatt N, Chapman LW, David so n MB (1981) Neural factor in K homeostasis of hyper- kalemic ureter-ligated dogs. Proc Soc Exp Biol Med 166:501-505 Higashi Y, Bello-Reuss E (1980) Dopamine decreases fluid reabsorption in straight portions of isolated proximal tub ule. Clin Res 28:749A Hillemand B, Leroy J, Joly JP, Le Grix A (1976) Effects of the nervous system on the kidney. Sem Hop Paris 52:958-963, 1163-1172 Hilton SM, Spyer KM (1980) Central nervous regulation of vascular resistance. Annu Rev Physiol 42:399-411 Himori N, Hayakawa S, Ishimori T (1979) Role of beta-1 and beta-2 adrenoceptors in isoproterenol induced renin release in conscious dogs. Life Sci 24:1953-1958 Himori N, Izumi A, Ishimori T (1980) Analysis of beta-adrenoceptors mediating renin release produced by isoproterenol in conscious dogs. Am J Physiol 238:F387- F393 Hoffman BB, Lefkowitz RJ (1980) Radioligand binding studies of adrenergic receptors: new insights into molecular and physiological regulation. Annu Rev Pharmacol Toxicol 20:581-608 Holdaas H, DiBona GF (1981) The role of left atrial receptors in the regulation of renin release in anesthetized dogs. Acta Physiol Scand 111:497-500 Holdaas H, DiBona GF, Kiil F (1981) Effect of low-level renal nerve stimulation on renin release from non filtering kidneys. Am J Physiol 241 :F 156-F 161 Hollenberg NK, Adams DF, Rashid A, Epstein M, Abrams HL, Merrill JP (1971) Renal vascular response to salt restriction in normal man. Circulation 43:845-851 Hollenberg NK, Adams DF, Solomon H, Chenitz WR, Burger BM, Abrams HL, Merrill JP (1975) Renal vascular tone in essential and secondary hypertension. Medicine 54:29-44 Hollingsead P, Willis LR (1980) Beta adrenergic receptor mediated renal tubular sodium reabsorption. Fed Proc 39:521 Honig A (1979) Electrolytes, body fluid volumes and renal function in acute hypoxic hypoxia: role of arterial chemoreceptors. Acta Physiol Pol (Suppl 18) 30:93-125 Honig A, Schrnidt M (1980) Kidney function during carotid chemoreceptor stimulation: influence of unilateral renal nerve section. In: Lichardus B, Schrier RW, Ponec J (eds) Hormonal regulation of sodium excretion. Elsevier/North Holland, Amsterdam, pp 93-98 Honig A, Schmidt M, Freyse EJ (1979) Influence of unilateral renal nerve section on the kidney: effects of carotid chemoreceptor stimulation. Acta Biol Med Get 38: 1647-1650 Houck CR (1951) Alterations in renal hemodynamics and function in separate kidneys during stimulation of renal artery nerves in dogs. Am J Physiol 167:523-530 Humphreys MH, Ayus JC (1978) Role of hemodynamic changes in the increased cation excretion after acute unilateral nephrectomy in the anesthetized dog. J Clin Invest 61:590-596 168 G.F. DiBona

Humphreys MH, Ayus JC, Stanton CJ (1980) Prevention by vagotomy or atropine administration of the hemodynamic changes occurring after acute unilateral nephrectomy in the dog. Circ Res 46:575-580 Iino Y, Brenner BM (1979) Stimulation of chloride transport by isoproterenol in isolated rabbit cortical coUecting tubule. Kindey Int 16:821 Iino Y, Flier S R, Brenner BM (1979) Effects of catecholamines on transepithelial potential difference and net water reabsorption in isolated rabbit cortical collecting tubule. Clin Res 27:418A Insel PA, Snavely MD (1981) Catecholamines and the kidney: receptors and renal function. Annu Rev Physio143:625-636 Jarecki M, Thoren PN, Donald DE (1978) Release of renin by the carotid baroreflex in anesthetized dogs. Role of cardiopulmonary vagal afferents and renal arterial pressure. Circ Res 42:614-619 Jarrott B, Louis WJ, Somers RJ (1979) Characteristics of [31-1] clonidine binding to an alpha adrenoceptor in membranes from guinea pig kindey. Br J Pharmacol 65: 663-670 Johns EJ (1979) Action of angiotensin I converting enzyme inhibitor on the control of renal function in the cat. Clin Sci 56:365-371 Johns EJ (1980) A comparison of the ability of two angiotensin II receptor blocking drugs, 1-sat, 8-ala angiotensin II and 1-sar, 8-ile angiotensin II, to modify the regulation of glomerular filtration rate in the cat. Br J Pharmacol 71:499-506 Johns EJ (1981) An investigation into the type of beta adrenoceptor mediating sympathetically activated renin release in the cat. Br J Pharmacol 73:749-754 Johns EJ, Lewis BA, Singer B (1976) The sodium retaining effect of renal nerve activity in the cat: role of angiotensin formation. Clin Sci 51:93-102 Johns E J, Murdock R, Singer B (1977) The effect of agniotensin I converting enzyme inhibitor on the release of prostaglandins by rabbit kidney in vivo. Br J Pharmacol 60:573-581 Johnson MD, Barger AC (1981) Circulating catecholamines in control of renal electrolyte and water excretion. Am J Physiol 240:F 192-F 199 Johnson MD, Malvin RL (1977) Stimulation of renal sodium reabsorption by angiotensin II. Am J Physiol 232 :F298-F306 Johnson MD, Fahri ER, Troen BR, Barger AC (1979a) Plasma epinephrine and control of plasma renin activity: possible extrarenal mechanisms. Am J Physiol 236:H854- H859 Johnson MD, Shier DN, Barger AC (1979b) Circulating catecholamines and control of plasma renin activity in conscious dogs. Am J Physio1236:H463-H470 Judy WV, Farrell SK (1979) Arterial barorecepor reflex control of sympathetic nerve activity in the spontaneously hypertensive rat. Hypertension 1:605-614 Judy WV, Thompson JR, Wilson MF (1971) Effect of isotonic saline loading on renal nerve activity and renal function. Physiologist 14:169 Judy WV, Watanabe AM, Henry DP, Besch HR Jr, Murphy WR, Hockel GM (1976) Sympathetic nerve activity. Role in regulation of blood pressure in spontaneously hypertensive rat. Circ Res (Suppl II) 38:21-29 Kaczmarczyk G, Eigenheer F, Gatzka M, Kuhl U, Reinhardt HW (1978) No relation between atrial natriuresis and renal blood flow in conscious dogs. Pfluegers Arch 373:49-58 Kaczmarczyk G, Schimmrick B, Mohnhaupt R, Reinhardt HW (1979) Atrial pressure and postprandial volume regulation in conscious dogs. Pfluegers Arch 381 : 143-150 Kaczmarczyk G, Echt M, Mohnhaupt R, Simgen B, Reinhardt H-W (1980) Postprandial volume regulation and renin angiotensin system in conscious dogs. Proc Int Union Physiol Sci 14:154 Kady NN (1974) Functional aspects of the renal innervation. Ph.D. Thesis, University of London The Functions of the Renal Nerves 169

Kahl FR, Flint JF, Szidon FP (1974) Influence of left atrial distention on renal vasomotor tone. Am J Physiol 226:240-246 Kalsner S, Chart CC (1979) Adrenergic antagonists and the presynaptic receptor hypothesis in vascular tissue. J Pharmacol Exp Ther 211:257-264 Kampine JP, Bosnjak Z J, Coon RI, Kostreva DR, Seagard JL, Zuperku EJ (1980) The role of cardiopulmonary reflexes in the regulation of sympathetic nerve activity. Pro c I nt Union Physiol S ci 14:154-155 Kaplan SA, Rapaport S (1951) Urinary excretion of sodium and chloride after splanchnicotomy. Effect on the proximal tubule. Am J Physiol 164:175-186 Kappagoda CT (1979) Atrial receptors and urine flow. In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge Univ, Cambridge, pp 193-212 Kappagoda CT, Linden RJ, Snow HM (1973) Effect of stimulating right atrial recep= tots on urine flow in the dog. J Physiol 235:493-502 Kappagoda CT, Linden RJ, Snow HM Whitaker EM (1974) Left atrial receptors and the antidiuretic hormone. J Physiol 221:427-440 Kappagoda CT, Linden RJ, Snow HM, Whitaker EM (1975) Effect of destruction of the posterior pituitary on the diuresis from left atrial receptors. J Physiol 244:757- 770 Kappagoda CT, Knapp MF, Linden RJ, Pearson MJ, Whitaker EM (1979a) Diuresis from left atrial receptors: effect of plasma on the secretion of the malphigian tubules of rhodnius prolixus. J Physiol 291:381-391 Kappagoda CT, Linden RJ, Sreeharan N (1979b) The role of renal nerves in the diuresis and natriuresis caused by stimulation of atrial receptors. J Physiol 287: 17P-18P Karim F, Kappagoda T (1980) Interaction of the influences of arterial baroreceptors and left atrial receptors on renal blood flow. Physiologist 23:42 Karim F, Kidd C, Malpus CM, Penna PE (1972) Effects of stimulation of the left atrial receptors on sympathetic efferent nerve activity. J Physiol 227:243-260 Kass DA, Sulzman FM, Fuller CA, Moore-Ede MC (1980) Renal responses to central vascular expansion are suppressed at night in conscious primates. Am J Physiol 239 :F343-F351 Katholi RE, Naftilan AJ, Oparil S (1980a) Importance of renal sympathetic tone in the development of DOCA-salt hypertension in the rat. Hypertension 2:266-273 Katholi RE, Winternitz SR, Oparil S (1981b) Role of the venal nerves in the pathogenesis of one-kidney renal hypertension in the rat. Circulation (Suppl III) 62: 111-88; Hypertension 3:404-409 Katholi RE, Winterntiz SR, Oparil S (1981) Alterations in peripheral sympathetic activity following renal denervation in one-kidney one-clip Goldblatt hypertension in the rat. Clin Res 29:358A Katz MA, Shear L (1975) Effects of renal nerves on renal hemodynamics. II. Renal denervation models. Nephron 14:390-397 Keeton TK, Campbell WB (1980) The pharmacologic alteration of renin release. Pharmacol Rev 32:81-212 Kendrick E, Oberg B, Wennergren G (1972) Vasoconstrictor fiber discharge to skeletal muscle kidney, intestine and skin at varying levels of arterial baroreceptor activity in the cat. Acta Physiol Scand 85:464-476 Kezdi P, Geller E (1968) Baroreceptor control of postganglionic sympathetic nerve discharge. Am J Physiol 214:427-435 Kim JK, Linas SL, Schrier RW (1979) Catecholamines and sodium transport in the kidney. Pharmacol Rev 31 : 169-178 Kinney MJ, Stein RM, Discala VA (1974) The polyuria of paroxysmal atrial tachycardia. Circulation 50:429-435 Kiowski W, Julius S (1978) Renin Response to stimulation of cardiopulmonary mechanorecpeotrs in man. J Clin Invest 62:656-663 170 G.F. DiBona

Kirchheim H (1976) Systemic arterial baroreceptor reflexes. Physiol Rev 56:100-176 Kirchheim HR, Gross R (1978) Response of renal blood flow and renal sympathetic nerve activity to baroreceptor and emotional stimuli in the conscious dog. In: Bauer RD, Busse R (eds) The arterial system. Springer, Berlin Heidelberg New York, pp 203-208 Klein LA, Liberman B, Laks M, Kleeman CR (1971) Interrelated effects of antidiuretic hormone and adrenergic drugs on water metabolism. Am J Physiol 221:1657- 1665 Kline RL, Mercer PF (1980a) Functional reinnervation and development of supersensitivity to NE after renal denervation. Am J Physiol 238:R353-R358 Kline RL, Mercer PF (1980b) Inhibition of angiotensin I convertin enzyme prevents hypertension due to aortic depressor nerve transection in rats. Physiologist 23: 64 Kline RL, Kelton PM, Mercer PF (1978) Effect of renal denervation on the development of hypertension in spontaneously hypertensive rats. Can J Physiol Pharmacol 56:818-822 Kline RL, Stuart PJ, Mercer PF (1980a) Effect of renal denervation on arterial pressure and renal norepinephrine concentration in Wistar-Kyoto and spontaneously hypertensive rats. C an J Physiol Ph armacol 58:1384-1388 Kline RL, Ciriello J, Mercer PF (1980b) Effect of renal denervation on changes in arterial pressure after aortic depressor nerve transection in the rat. Fed Proc 39: 962 Knapp MF, Linden RJ, Mary DASG, Pearson MJ (1980) Role of angiotensin II and bradykinin in the diuresis caused by stimulation of atrial receptors. Q J Ex Physiol 65:335 -347 Knox FG, Burnett JC Jr, Kohan DE, Spielman WS, Strand JC (1980) Escape from the sodium-retaining effects of mineralocorticoids. Kidney Int 17:263-276 Knuepfer MM, Mohrland JS, Shaffer RA, Gebhart GF, Johnson AK, Brody MJ (1980) Effects of afferent renal nerve stimulation and baroreceptor activation on unit activity in the anteroventral third ventricle region. Red Proc 39:837 Koepke JP, Grignolo A, Obrist PA (1981) Decreased urine and sodium excretion rates during signalled shock-avoidance in dogs: role of beta-adrenergic receptors. Fed Proc 40:553 Kopp U (1980) Mechanisms involved in the neural control of renin release. Ph.D. Dissertation, University of Goteborg, Goteborg, Sweden Kopp U, Aurell M, Nilsson IM, Ablad B (1980a) The role of beta-1 adrenoceptors in the renin release response to graded renal sympathetic nerve stimulation. Pfluegers Arch 387:107-113 Kopp U, Hjemdahl P, Eriksson B-M, Bradley T (1980b) Release of endogenous noradrenaline and dopamine from blood perfused canine kidney in situ: effects of metoprolol, phenoxybenzamine and indomethacin. Naunyn Schmiedebergs Arch Pharmacol (Suppl) 313:R21 Kopp U, Aurell M, Sjolander M, Ablad B (1981a) The role of prostagiandins in the alpha and beta-adrenoceptor mediated renin release response to graded renal nerve stimulation. Pfluegers Arch 391 : 1-8 Kopp U, AureU M, Svensson L, Ablad B (1981b) Effects of prenalterol, a beta-1 adrenoceptor agonist, on renal function in anesthetized dogs. Acta Pharmacol Toxico149:230-235 Kostreva DR, Castaver A, Kampine JP (1980) Reflex effects of hepatic baroreceptors on renal and cardiac sympathetic nerve activity. Am J Physiol 238:R390-R394 Kostreva DR, Seagard JL, Castaner A, Kampine JP (1981) Reflex effects of renal afferents on the heart and kidney. Am J Physiol 241 :R286-R292 Kottra G, Takacs L (1980) Non-occurrence of a reno-renal vasoconstrictor reflex induced by acetylcholine in anesthetized dogs. Proc Int Union Physiol Sci 14: 525 The Functions of the Renal Nerves 171

K0ttra G, Albert K, Takacs L (1978) Effects of isotonic volume expansion on renal nervous activity and renal function in the rat. Renal Physiol 1:296-300 Kurkus J, Sadowski J, Gellert R, Krus S (1980) Influence of renal denervation on urine concentration in awake and anesthetized dogs. Eur J Clln Invest 10:463- 467 La Grange RG, Mitchell SW (1978) Evidence for a neural component of the saluretic- diuretic response to atrial tachycardia. Clin Res 26:468A La Grange RG, Sloop CH, Schmid HE (1973) Selective stimulation of renal nerves in the anesthetized dog. Circ Res 33:704-712 Lappe RW, Henry DOP, Willis LR (1980a) Mechanism of renal tubular secretion of norepinephrine in the rabbit. J Pharmacol Exp Ther 125:443-449 Lappe RW, Henry DP, Willis LR (1980b) Effects of renal sympathetic nerve activity on the urinary excretion of endogenous norepinephrine. Pharmacologist 22:257 Larsson C, Weber P, Anggard E (1974) Arachidonic acid increases and indomethacin decreases plasma renin activity in the rabbit. Eur J Pharmacol 28:391-394 Lazzara R, Carson RP, Klain GJ (1970) Diuresis initiated by coronary stretch receptors: a neurogenic mechanism for intravascular volume homeostatsis. Fed Proc 29: 460 Leavitt ML, Miller RE, Kotchen TA (1980) Suppression of stimulated plasma renin by clonidine in the dog. Hypertension 2:187-191 Ledsome JR, Linden RJ (1968) The role of left atrial receptors in the diuretic response to left, atrial distension. J Physiol 198:487-503 Lees P (1968) The influence of beta adrenoceptive receptor blocking agents on urinary function in the rat. Br J Pharmacol 34:429-444 Levinsky NG (1979) The renal kallikrein-kinin system. Circ Res 44:441-459 Liang CC (1979) The influence of hepatic portal circulation on urine flow. J Physiol 214:571-581 Liard JF (1976) Renal denervation delays blood pressure increase in the spontaneously hypertensive rat. Experientia 33:339-342 Lifschitz MD (1978) Lack of a role for the renal nerves in renal sodium reabsorption in conscious dogs. Clin Sci 54:567-572 Linden RJ (1975) Reflexes from the heart. Proc Cardiovasc Dis 18:102-221 Linden RJ (1978) Neurocirculatory control of sodium and water excretion. In: Dickenson C J, Marks J (eds) Developments in cardiovascular medicine. MTP, Lan- caster, pp 191-203 Linden RJ, Sreeharan N (1979) Does the renal humoral response to stimulation of atrial receptors include a natriuresis? J Physiol 291:43P-44P Linden RJ, Mary DASG, Weatherill D (1979) The response of renal nerve inhibition of atrial receptors during changes in carotid sinus pressure in the dog. J Physiol 290:32P-33P Linden RJ, Mary DASG, Weatherill D (1980) The nature of the atrial receptors responsible for a reflex decrease in activity in renal nerves in the dog. J Physiol 300: 31-40 Livnat A, Zehr JE (1980) Reflex inhibition of renin secretion and induced renal vasodilatation following acute left circumflex occlusion in dogs. Physiologist 23:127 Ljungqvist A (1975) Effect of angiotensin infusion, sodium loading and sodium restriction on renal and cardiac sympathetic nerves. Acta Pathol Microbiol Scand 83: 661-668 Lloyd TC, Friedman JJ (1977) Effect of a left atrium-pulmonary vein baroreflex on peripheral vascular beds. Am J Physiol 233 :H587-H591 MacFarlane MD (1970) A renorenal vasoconstrictor reflex induced by acetylcholine. Am J Physiol 218:851-856 Mahoney LT, Haywood JR, Packwood WJ, Johnson AK, Brody MJ (1978) Effect of anteroventral third ventricle (AV3V) lesions on regional hemodynamic responses to renal afferent nerve stimulation. Circulation (Suppl II) 58:11-68 172 G.F. DiBona

Mancia G, Donald DE, Shepherd JT (1973) Inhibition of adrenergic outflow to peripheral blood vessels by vagal afferents from the caridiopulmonary region in the dog. Circ Res 33:713-721 Mancia G, Romero JC, Strong CG (1974) Neural influence on canine renal prostaglandin secretion. Acta Physiol Lat Am 24:555-560 Mancia G, Shepherd JT, Donald DE (1976) Interplay among carotid sinus, cardiopulmonary and carotid body reflexes in dogs. Am J Physiol 230:19-24 Mason JM, Ledsome JR (1974) Effects of obstruction of the mitral orifice or distention of the pulmonary vein-atrial junction on renal and hind limb vascular resistance in the dog. Circ Res 35:24-32 McCall RB, Gebber GL (1976) Differential effect of baroreceptor reflexes and clonidine on frequency components of sympathetic discharge. Eur J Pharrnacol 36: 69-78 McGiff JC, Crowshaw K, Terragno NA, Linigro A J, Strand JC, WiUiamson MA, Lee JB, Ng, KKF (1970) Prostagiandin-like substances appearing in canine renal venous blood during renal ischemia. Circ Res 27:765-782 McGiff JC, Crowshaw K, Terragno NA, Malik KU, Lonigro AJ (1972) Differential effect of noradrenaline and renal nerve stimulation on vascular resistance in the dog kidney and the release of a prostaglandin E-like substance. Clin Sci 42:223-233 Mills IH, Osbaldiston GW (1968) The effect of stretch of the fight atrium on arterial pressure and renal function in the dog. J Physiol 197:40-41P Minneman KP, Pittman RN, Molinoff PB (1981) Beta-adrenergic receptor subtypes: properties, distribution and regulation. Annu Rev Neurosci 4:419-461 Mitchell GAG (1950) The nerve supply ofthe kidneys. Acta Anat 10:1-37 Montgomery S, Jose P, Spiro P, Slotkoff L, Eisner G (1979) Regional differences in the canine kdiney cortex. Proc Soc Exp Biol Med 162:260-263 Morel F (1981) Sites of hormone action in the mammalian nephron. Am J Physiol 240:F 159-F 164 Morel F, Imbert-Teboul M, Chabardes D (1981) Distribution of hormone-dependent adenylate cyclase in the nephron and its physiological significance. Annu Rev Physiol 43: 569-581 Morgunov N (1980) Norepinephrine and dopamine release by renal nerves. Ph.D. Thesis. University of Toronto Morgunov N, Baines AD (1981a) Renal nerves and catecholamine excretion. Am J Physiol 240:F75-F81 Morgunov N, Baines AD (1981b) Vagal afferent activity and renal nerve release of dopamine. Clin Res 29:471A Moss NG, Harrington WW (1980) Renal nerves and the reflex control of sodium excretion. Clin Res 28:535A Moss NG, Harrington WW (1981) Reinnervation of the kidney following nerve crush. Fed Proc 40:553 Mroczek WJ, Davidov M, Gabrilovich L, Finnerty FA (1970) The response of hypertensive patients to a hypertonic saline load after beta-adrenergic blockade. Clin Res 18:511 Mullins MM, Banks RO (1976) Age related changes in sodium excretion in saline loaded spontaneously hypertensive rats. Am J Physiol 231 : 1364-1370 Mursch DA, Bishop VS (1980) Effects of vagal cold block on plasma renin activity and renin secretion in the conscious dog. Fed Proc 39:840 Myers BD, Deen WD, Brenner BM (1975) Effects of norepinephrine and angiotensin II on the determinants of glomerular ultrafiltration and proximal tubule fluid reabsorption in the rat. Circ Res 37:101-110 Nagatsu T, Rurt LA, Dequattro V (1969) The activity of tyrosine hydroxylase and related enzymes of catecholamine synthesis and metabolism in dog kidney: effect of denervation. Biochem Pharmacol 18:1441 - 1446 The Functions of the Renal Nerves 173

Nies AS, McNeil JS, Schrier RW (1971) Mechanism of increased sodium reabsorption during propranolol administration. Circ 44: 596-604 Niijima A (1971) Afferent discharges from arterial mechanoreceptors in the kidney of the rabbit. J Physiol 219:477-485 Niijima A (1972a) Studies on the blood pressure sensitive receptors in the rabbit kidney in vivo. Jpn J Physiol 22:433-440 Niijima A (1972b) The effect of discharges in renal nerves on the activity of arterial mechanoreceptors in the kidney in rabbit. J Physiol 222:335-343 Niijima A (1975) Observation on the localization of mechanoreceptors in the kidney and afferent nerve fibers in the renal nerves in the rabbit. J Physiol 245:81-90 Niijima A (1976) Baroreceptor effects on renal and adrenal nerve activity. Am J Physio1230:1733-1736 Ninomiya I, Fujita S (1976) Reflex effects of thermal stimulation on sympathetic nerve activity to skin and kidney. Am J Physiol 230:271-278 Ninomiya I, Irisawa H, WooUey G (1974) Intestinal mechanoreceptor reflex effects on sympathetic nerve activity to intestine and kidney Am J Physiol 227:684-691 Noland PL, Reid IA (1978) Mechanism of suppression of renin secretion by clonidine in the dog. Circ Res 42:206-211 Nomura G, Kurosaki M, Takabatake T, Kibe Y, Takeuchi J (1972) Reinnervation and renin release after unilateral renal denervation in the dog. J Appl Physiol 33:649- 655 Nomura G, Kibe Y, Arai S, Uno D, Takeuchi J (1976) Distribution of intrarenal blood flow after renal denervation in the dog. Nephron 16:126-133 Nomura G, Takabatake T, Arai S, Uno D, Shimao M, Hattori N (1977) Effect of acute unilateral renal denervation on tubular sodium reabsorption in the dog. Am J Physiol 232 :F 16-F 19 Nomura G, Arai S, Uno D, Shimao M, Takata M, Takabatake T, Hattori N (1978) Effect of propranolol on sodium reabsorption and the renal circulation. Renal Physiol 1:132-139 Noresson E, Ricksten S-E, Thoren P (1979) Left atrial pressure in normotensive and spontaneously hypertensive rats. Acta Physiol Scand 107:9-12 NorveU JE (1968) The aorticorenal ganglion and its role in renal innervation. J Comp Neurol 133:101-112 NorveU JE (1970) Renal nerves: are they essential? N Engl J Med 283:261 Norvell JE, Weitsen HA, Sheppek GG (1970) The intrinsic innervation of human renal homotransplants. Transplantation 9 : 168-176 Oates NS, Ball SG, Perkins CM, Lee MR (1979) Plasma and urine dopamine in man given sodium chloride in the diet. Clin Sci 56:261-264 Oberg B, White S (1970) The role of vagal cardiac nerves and arterial baroreceptors in the circulatory adjustments to hemorrhage in the cat. Acta Physiol Scand 80: 395 -403 Oliver JA, Pinto J, Sciacca RR, Cannon PJ (1980a) Basal norepinephrine overflow into the renal vein: effect of renal nerve stimulation. Am J Physiol 239 :F371-F377 Oliver JA, Pinto J, Sciacca RR, Cannon PJ (1980b) Increased renal secretion of norepinephrine and prostaglandin E 2 during sodium depletion in the dog. J Clin Invest 66:748-756 Olson RD, Nies AS, Gerber JG (1980a) Macula densa mediates renal alpha adrenocep- tot stimulated renin release. Circ (Suppl III) 62 :Ill-88 Olson RD, Nies AS, Gerber JG (1980b) Canine renal beta-2 adrenoceptor activation increases renin secretion. Circ (Suppl III) 62:111-223 Olson RD, Skoglund ML, Nies AS, Gerber JG (1980c) Prostaglandins mediate the macula densa stimulated renin release. In: Samuelsson B, Ramwell P, Paoletti R (eds) Advances in prostaglandin and thromboxane research, vol 7. Raven, New York, pp 1135-1137 174 G.F. DiBona

Olson U, Magnussen M, Eilersten E (1976) Prostaglandins, a link between renal hydro- and hemodynamics in dogs. Acta Physiol Seand 97:369-376 Opgenroth TJ, Wappel M, Zehr JE (1980) Failure of indomethacin to suppress the renin release to salt depletion in dogs. Fed Proc 39:497 Osborn JL, DiBona GF (1979) Effect of low level renal nerve stimulation during aortic constriction on renin secretion in filtering and non-filtering kidneys. Physiol- ogist 22:97 Osborn JL, DiBona GF, Thames MD (1981 a) Beta-1 receptor mediation of renin secretion elicited by low frequency renal nerve stimulation. J Pharmacol Exp Ther 216: 265 -269 Osborn JL, DiBona GF, Thames MD (1982) Role of alpha adrenoceptors mediating renin secretion. Am J Physiol 242 :F620-F626 Pang PKT, Uchiyama M, Sawyer WH (1982) Endocrine and neural control of amphibian renal functions. Fed Proc 41:2365-2370 Pappenheim S (1840) Arch of Anat Physiol U Wissensch Med 7:534. In: Baker R, Tarabulcy E (1966) Effect of contralateral nephrectomy and renal nerves on renal function. Med Ann District Columbia 35:467-469 Pastoriza E (1979) Effect of alpha-adrenergic stimulation and blockade in the proximal convoluted tubule of the rat. Kidney Int 16:831 Pearson JE, Williams RL (1968) Analysis of direct renal actions of alpha and beta adrenergic stimulation upon sodium excretion compared to acetylcholine. Br J Pharamcol Chemother 33:223 -241 Pelletier CL, Shepherd JT (1975a) Relative infouence of carotid baroreceptors and muscle receptors in the control of renal and hindlimb circulations. Can J Physiol Pharmacol 53:1042-1049 Pelletier CL, Shepherd JT (1975b) Effect of hypoxia on vascular response to the carotid baroreflex. Am J Physiol 228:331-336 Pettinger W, Sanchez A, Gandler T, Sanchez J, Saavedra J (1981) Dietary sodium regulates abnormal renal alpha adrenergic receptors in the Dahl hypertensive rat. Clin Res 29:276A Pines IL (1960) The electrophysiolocial characteristic of the afferent connections of the kidney with the central nervous system. Sechenov Physiol J USSR 46:1622- 1630 Pines YL (1966) Fatigue in the receptors of the kidneys. Bull Exp Biol Med 62:16 -21 Pines YL (1969) Electrophysiological investigation of the effects of chemical substances in the urine on renal receptors. Bull Exp Biol Med 67:3-7 Pogglitsch H (1973) Die neurale Regulation der renalen H~imodynamik, Wasser- und Natriumausscheidung. Wiener Med Wochenschr (Suppl 3) 123:2-16 Polhemus RE, Hall DA (1980) Effect of catecholamines on the potential difference and chloride efflux in the mouse thick ascending limb of Henle's loop. Proc Am Soc Nephrol 13:146A Pomeranz BH, Birtch AG, Barger AC (1968) Neural control of intrarenal blood flow. Am J Physiol 215:1067-1081 Powis DA, Donald DE (1979) Involvement of renal alpha and beta-adrenoceptors in release of renin by carotid baroreflex. Am J Physiol 236:H580-H585 Prosnitz EH, DiBona GF (1978) Effect of decreased renal sympathetic nerve activity on renal tubular sodium reabsorption. Am J Physiol 235 :F557-F563 Prosnitz EH, DiBona GF (1980) Effects of propranolol on renal function. Clin Res 28:64A Prosnitz EH, Zambraski EJ, DiBona GF (1977) Mechanism of intrarenal blood flow distribution after carotid artery occlusion. Am J Physiol 232 :F 167-F 172 Purtock RV, Colditz JH yon, Seagard JL, Igler FO, Zuperku EJ, Kampine JH (1977) Reflex effects of thoracic sympathetic afferent nerve stimulation on the kidney. Am J Physio1233:H580-H586 The Functions of the Renal Nerves 175

Quinby WC (1916) The junction of the kidney when deprived of its nerves. J Exp Med 25:535-548 Rand MJ, Majewski H, Medgett IC, McCulloch MW, Story DF (1980) Prejunctional receptors modulating autonomic neuroeffector transmission. Circ Res (Supp I) 46:I-70-1-76 Recordati GM, Spielman WS (t977) Effects of fluid volume expansion on renal sympathetic efferent nerve activity in the rat. Fed Proc 36:487 Recordati GM, Moss NG, Waselkov L (1978) Renal chemoreceptors in the rat. Circ Res 43:534-543 Recordati G, Genovesi S, Cerati D, Dicintio R (1980a) Reno-renal and reno-adrenal reflexes in the rat. Clin Sci 59:323S-325S Recordati GM, Moss NG, Genovesi S, Rogenes PR (1980b) Renal receptors in the rat sensitive to chemical alterations of their environment. Circ Res 46:395-405 Reid IA, Schrier RW, Early LE (1972) An effect of extrarenal beta-adrenergic stimulation on the release of renin. Clin Invest 51:1861-1869 Reid IA, Morris BJ, Ganong WF (1978) The renin-angiotensin system. Annu Rev Physio140:377-410 Reimann KA, Weaver LC (1980) Contrasting reflexes evoked by chemical activation of cardiac afferent nerves. Am J Physiol 239 :H316-H325 Reinhardt HW, Behrenbeck DW (1967) Untersuchungen an wachen Hunden tiber die Einstellung der Natriumbilanz. I. Die Bedeutung des Extracellularraumes ftir die Einstellung der Natrium-Tagesbilanz. Pfluegers Arch 295:266-279 Reinhardt H-W, Kaczmarczyk G, Mohnhaupt R, Simgen B (1980a) The possible mech- anims of atrial natriuresis - experiments on chronically instrumented dogs. In: Lichardus B, Schrier RW, Ponec J (eds) Hormonal regulation of sodium excretion. Elsevier/North Holland, Amsterdam, pp 43-51 Reinhardt H-W, Kaczmarczyk G, Mohnhaupt R, Simgen B, Wegener S (1980b) Is the control of sodium excretion partly due to signals from receptors located in the left atrium of the heart? Proc Int Union Physiol Sci 14:222 Reynolds GP, Ceasar PM, Ruthven CRJ, Sandier M (1978) The effect of urinary pH and flow rate on monoamine output. Clin China Acta 84:225-231 Richards AN, Plant OH (1922) Urine formation in the perfused kidney. The influence of adrenalin on the volume of the perfused kidney. Am J Physiol 59:184-190 Ricksten S-E (1980) Function of cardiac mechanoreceptors in primary hypertension: experimental studies in spontaneously hypertensive rats. Doctoral Thesis, Universi- ty of Goteborg, Goteborg, Sweden Ricksten S-E, Thoren P (1980) Reflex inhibiton of sympathetic activity during volume load in awake norrnotensive and spontaenously hypertensive rats. Acta Physiol Scand 110:77-82 Ricksten S-E, Noresson E, Thoren P (1979) Inhibition of renal sympathetic nerve traffic from cardiac receptors in normotensive and spontaneously hypertensive rats. Acta Physiol Scand 106:17-22 Ricksten S-E, Yao T, DiBona GF, Thoren P (1981) Renal nerve activity and exaggerated natriuresis in conscious spontaneous hypertensive rats. Acta Physiol Scand 112: 161-167 Robie NW (1979) Presynaptic inhibition of canine renal adrenergic nerves by acetylcholine in vivo. Am J Physiol 237 :H326-H331 Robie NW (1980) Evaluation of presynaptic alpha-receptor function in the canine renal vascular bed. Am J Physiol 239:H422-H426 Robie NW (1981) Modulation by histamine agonists and antagonists of renal adrenergic neuronal vasoconstriction in vivo. Fed Proc 40:242 Rocchini AP, Barger AC (1979) Renin release with carotid occlusion in the conscious dog: role of renal arterial pressure. Am J Physiol 236:H108-H111 Rocchini AP, Cant JR, Barger AC (1977) Carotid sinus reflex in dogs with low to high sodium intake. Am J Physiol 233 :H 196-H202 176 G.F. DiBona

Rogenes PR, Gottschalk WC (1980) Denervation diuresis and natriuresis in conscious fast. Proc Am Soc Nephrol 13:148A Romero JC, Dunlap CL, Strong CG (1976) The effect of indomethacin and other anti- inflammatory drugs on the renin-angiotensin system J Clin Invest 58:282-288 Rouot BR, Snyder SH (1979) [3H]-paraaminoclonidine: a novel ligand which binds with high affinity to alpha adrenergic receptors. Life Sci 25:769-774 Rumpf KW, Frenzel S, Lowtiz HD, Scheler F (1975) The effect of indomethacin on plasma renin activity in man under normal conditions and after stimulation of the renin angiotensin system. Prostaglandins 10:641-648 Sadowski J, Kurkus J, Gellert R (1979a) Denervated and intact kidney responses to saline load in awake and anesthetized dogs. Am J Physiol 237 :F262-F267 Sadowski J, Kurkus J, Gellert R (1979b) Reinvestigation of denervation diuresis and natriuresis in conscious dogs. Arch Int Physiol Biochem 87:663-672 Sadowski J, Kurkus J, Gellert R (1980) Have renal nerves a major role in control of sodium excretion? In: Lichardus B, Schrier RW, Ponec J (eds) Hormonal regulation of sodium excretion. Elsevier/North Holland, Amsterdam, pp 33-42 Sawchenko PE, Friedman MI (1979) Sensory functions of the liver - a review. Am J Physiol 236:R5-R20 Schad H, Seller H (1975) A method for recording autonomic nerve activity in unanesthetized, freely moving cats. Brain Res 100:425-430 Schad H, Seller H (1976) Reduction of renal nerve activity by volume expansion in conscious cats. Pfluegers Arch 363:155-159 Schiffrin EL, Garcia R, Gutkowska J, Boucher R, Genest J (1980) Role of prostaglandins, beta-adrenoceptors and the central nervous control of renin release in conscous sodium-depleted rats. Proc Soc Exp Biol Med 165:151-154 Schneider E, McLane-Vega L, Hanson R, Childers J, Gleason S (1978) Effect of chronic bilateral renal denervation on daffy sodium excretion in the conscious dog. Fed Proc 37:645 S chram LP, Carlson DE (1975) Inhibition of renal vasoconstriction by elevated ureteral pressure. Am J Physiol 228:1126-1133 Schrier RW (1974) Effects of adrenergic nervous system and catecholamines on systemic and renal hemodynamics, sodium and water excretion, and renin secretion. Kidney Int 6:291-306 Schrier RW, Humphreys MH, Ufferman RC (1971) Role of cardiac output and the autonomic nervous system in the antinatriuretic response to acute constriction of the thoracic superior vena cava. Circ Res 29:490-498 Schultz HD, Fater DC, Sundet WD, Goetz KL (1980) Renal responses to partial obstruction at various points in the intrathoracic circulation of conscious dogs. Physiologist 23:129 Scott CK, Vanderwende C (1980) The identification of [3H] apomorphine binding sites in dog renal cortex membrane preparations. Fed Proc 38:1007 Seymour AA, Zehr JE (1979) Influence of renal prostaglandin synthesis on renal control mechanisms in the dog. Circ Res 45:13-25 Shvalev VN (1966) Problems in the morphology and nature of renal innervation. Fed Proc (Transl Supp) 25 :T595-T600 Simgen B, Kaczmarczyk G, Mohnhaupt R, Schulze G, Reinhardt HW (1979) The contribution of the renal nerves to adjustments of the sodiur~ balance. Pfluegers Arch 382:R17 Sivananthan N, Kappagoda CT, Linden RJ (1981) The nature of atrial receptors responsible for the increase in urine flow caused by distension of the left atrium in the dog. Q J Exp Physiol 66:51-59 Slick GL, DiBona GF, Kaloyanides GJ (1974) Renal sympathetic nerve activity in sodium retention of acute caval constriction. Am J Physiol 226:925-932 Slick GL, Aguilera AJ, Zambraski EJ, DiBona GF, Kaloyanides GJ (1975) Renal neuroadrenergic transmission. Am J Physiol 229:60-65 The Functions of the Renal Nerves 177

Smith HW (1937) The physiology of the kidney. Oxford Univ, New York, pp 245- 246 Smith HW (1951) The kidney: structure and function in health and disease. Oxford Univ, New York, pp 424-596 Smith HW, Chasis H, Goldring W, Ranges HA (1940) Glomerular dynamics in the normal human kidney. J Clin Invest 19:751 Spencer HW, Yarger WE (1977) The effect of time and anesthesia on denervation natriuresis in the rat. Clin Res 25:43A Spyer KM (1981) The neural organization and control of the baroreceptor reflex. Rev Physiol Biochem Pharmacol 88:23-124 Starke K (1977) Regulation of noradrenaline release by presynaptic receptor systems. Rev Physiol Biochem Pharmacol 77:1-124 Starke K (198 l a) Alpha adrenoceptor subclassification. Rev Physiol Biochem Pharma- col 88:199-236 Starke K (1981 b) Presynaptic receptors. Annu Rev Pharmacol Toxicol 21:7-30 Stein JH, Osgood RW, Ferris TF (1972) The effect of beta adrenergic stimulation on proximal tubular sodium reabsorption. Proc Soc Exp Biol Med 141:901-905 Steiner RW, Blantz RC (1979) Acute reversal by saralasin of multiple intrarenal effects of angiotensin II. Am J Physiol 237 :F386-F391 Steiner RW, Tucker BJ, Blantz RC (1979) Glomerular hemodynamics in rats with chronic sodium depletion: Effect of saralasin. J Clin Invest 64:503-512 Stella A, Dampney RAL, Golin R, Zanchetti A (1978a) Afferent vagal control of renin release in the anesthetized cat. Circ Res (Supp I) 43:1-107-1-111 Stella A, Dampney RAL, Golin R, Zanchetti A (1978b) Differences in reflex control of arterial pressure and renin release during head-up tilting in the cat. Clin Sci Mol Med 55:1795-1815 Stephenson RK, Sole MJ, Baines AD (1982) Neural and extraneural catecholamine production by rat kidneys. Am J Physiol 242 :F261-F266 Stinson JM, Barnes AB, Zakheim RM, Chfinoskey JE, SpineUi FR, Barger AC (1969) Reflex cholinergic vasodilatation during renal artery constriction in the unanesthetized dog. Am J Physiol 217:239-246 Stinson JM, Mootry P J, Jackson CG, Gates HO, Scott MT (1976) Renal vasodilatation in response to coronary artery ligation in the dog. Clin Exp Pharmacol Physiol 3: 191-194 Stitzer SO, Malvin RL (1975) Right atrium and renal sodium excretion. Am J Physiol 228:184-190 Standhoy JW, Schneider EG, Willis LR, Knox FG (1974) Intrarenal effects of phenoxybenzamine on sodium reabsorption. J Lab Clin Med 83:263-270 Struyker-Boudier HAJ, Van Essen H, Sinits JFM, Evenwel R (1979) Exaggerated diuresis and natriuresis in conscious spontaneously hypertensive rats. Therapiewoche 29:7740-7743 Stryuker-Boudier HAJ, Smits JFM, Evenwel R (1980) Exaggerated diuresis and natriuresis in conscious SHR. Int Soc Hypertension 7:128 Szalay L, Bencsath P, Takacs L (1977a) Effect of splanchnicotomy on the renal excretion of inorganic phosphate in the anesthetized dog. Pfluegers Arch 367:283-286 Szalay L, Bencsath P, Takacs L (1977b) Effect of splanchnicotomy on the renal excretion of para-aminohippuric acid in the anesthetized dog. Pfluegers Arch 367: 287-290 Szalay L, Bencsath P, Takacs L (1977c) Effect of splanchnicotomy on the renal excretion of d-glucose in the anesthetized dog. Pfluegers Arch 369:79-84 Szalay L, Bencsath P, Takacs L (1977d) Impaired proximal tubular transport functions in anesthetized splanchnicotomized dogs. Experientia 33:42-43 Szalay L, Lang E, Bencsath P, Mohai L, Fischer A, Takacs L (1977e) Effect of splanchnicotomy on the renal excretion of uric acid in anesthetized dogs. Pfluegers Arch 368:185-188 178 G.F. DiBona

Szalay L, Colindres RE, Jackson R, Adkinson JT, Lassiter WE, Gottschalk CW (1980) Phosphate transport in chronically denervated rat kidney. Proc Am Soc Nephrol 13:10A Szenasi G, Bencsath P, Lehoczky E, Takacs L (1981) Tubular transport and urinary excretion of phosphate after renal denervation in the anesthetized rat. Am J Physiol 240:F481-F486 Taher MS, McLain LG, McDonald KM, Schrier RW (1976) Effect of beta-adrenergic blockade on renin response to renal nerve stimulation. J Clin Invest 57:459-465 Takacs L, Bencsath P, Szalay L (1978) Decreased proximal tubular transport capacity after renal sympathectomy. Proc Int Cong Nephrol 8:553-558 Takacs L, Bencsath P, Szenasi G (1979) Effect of acute and chronic unilateral renal denervation on excretion and Tm of inorganic phosphate in normal and TPTX rats. Upsalla J Med Sci (Suppl) 26:71 Takeshita AL (1978) Neurogenic contribution to hindquarters vasoconstriction during high sodium intake in Dahl strain of genetically hypertensive rat. Circ Res 43:I86- 190 Takeshita A, Mark AL, Brody MJ (1979) Prevention of salt-induced hypertension in the Dahl strain by 6-hydroxydopamine. Am J Physio1236:H48-H52 Takeuchi J, Uchida E, Nakayama S, Takeda T, Yagi S, Inoue G, Ueda H (1961) Ex- perimental studies on the nervous control of the renal circulation. Jpn Heart J 2:65-75 Takeuchi J, Iino S,. Hanada S, Sakal S, Oya N, Kitamura K (1964) Experimental studies on the nervous control of the renal circulation-effect of the electrical stimulation of the spinal cord on the renal circulation. Jpn Heart J 5:69-80 Takeuchi J, Iino S, Hanada S, Sakai S, Oya N, Kitamura K (1965) Experimental studies on the nervous control of the renal circulation. Jpn Heart J 6:543-557 Takeuchi J, Ohya N, Sakai S, Nakamura H, Nohara T, Hirasawa K, Shinoda A (1968) Nervous control of the renal tubular function. Jpn Heart J 9:564-572 Takeuchi J, Aoki S, Nomura G, Mizumura Y, Shimizu H, Kubo T (1971) Nervous control of renal circulation - on the existence of sympathetic cholinergic fibers. J Appl Physiol 31:686-692 Thames MD (1978) Contribution of cardiopulmonary baroreceptors to the control of the kidney. Fed Proc 37 : 1209-1213 Thames MD (1979) Acetylstrophanthidin-induced reflex inhibition of canine renal sympathetic nerve activity mediated by cardiac receptors with vagal afferents. Circ Res 44:8-15 Thames MD, Abboud FM (1979a) Reflex inhibition of renal sympathetic nerve activity during myocardial ischemia mediated by left ventricular receptors with vagal afferents in dogs. J Clin Invest 63:395-402 Thames MD, Abboud FM (1979b) Interaction of somatic and cardiopulmonary receptors in control of renal circulation. Am J Physiol 237 :H560-H565 Thames MD, DiBona GF (1979) Renal nerves modulate the secretion of renin mediated by nonneural mechanisms. Circ Res 44:645-652 Thames MD, Schmid PG (1979) Cardiopulmonary receptors with vagal afferents tonically inhibit ADH release in the dog. Am J Physiol 237 :H299-H304 Thames MD, Klopfenstein HS, Abboud FM, Mark AL, Walker JL (1978) Preferential distribution of inhibitory cardiac receptors with vagal afferents to the inferoposterior wall of the left ventricle activated during coronary occlusion in the dog. Circ Res 43:512-519 Thames MD, Osborn JL, DiBona GF (1980a) Renin release mediated solely by renal nerves; inhibition by blockade of prostaglandin synthesis. Circulation (Suppl III) 62 :III-122 Thames MD, Waickman LA, Abboud FM (1980b) Sensitization of cardiac receptors (vagal afferents) by iutracoronary acetylstrophanthidin. Am J Physiol 239:H628- H635 The Functions of the Renal Nerves 179

Thoren P (1979) Role of cardiac vagal C-fibers incardiovascular control. Rev Physiol Biochem Pharmacol 86:1-94 Thoren P, Ricksten S-E (1979) Recordings of renal and splanchnic sympathetic nervous activity in normotensive and spontaneously hypertensive rats. Clin Sci 57: 197s-199s Thoren P, Noresson E, Ricksten S-E (1979a) Resetting of cardiac C-fiber endings in the spontaneously hypertensive rat. Acta Physiol Scand 107:13-18 Thoren P, Noresson E, Ricksten S-E (1979b) Cardiac reflexes in normotensive and spontaneously hypertensive rats. Am J Cardio144:884-888 Touw KB, Haywood JR, Shaffer R,A, Brody MJ (1980) Contribution of the sympathetic nervous system to vascular resistance in conscious young and adult spontaneously hypertensive rats. Hypertension 2:408-418 Tucker B J, Blantz RC (1978) Inhibition of tubuloglomerular feedback induced reduction in nephron filtration rate with saralasin. Kidney Int 14:784A Tucker B J, STeiner RW, Gushwa L, Blantz RC (1978) Studies on the tubuloglomerular feedback system in the rat. J Clin Invest 62:993-1004 Uchida Y (1979) Mechanisms of excitation of cardiac sympathetic afferents. In: Hainsworth R, Kidd C, Linden RJ (eds) Cardiac receptors. Cambridge Univ, Cam- bridge, pp 301-318 Uchida Y, Kamisaka K, Ueda H (1971) Two types of renal mechanoreceptors. Jpn Heart J 12:233-241 Ueda H, Uchida Y (1968) Afferent impulses in the renal nerves. Jpn Heart J 9:517- 519 Ueda H, Uchida Y, Kaisaka K (1967) Mechanism of the reflex depressor effect by kidney in dog. Jpn Heart J 8:597-606 Ueda H, Uchida Y, Kamisaka K (1971) Responses of renal mechanoreceptors to vaso- pressor substances. Jpn Heart J 12:347-353 Ueda J, Kishimoto T, Shimizu H, Yamamoto K (1968) Renal vascular response to ganglionic stimulants in the dog. Jpn Circ J 32:705-714 U'Prichard DC, Snyder SH (1979) Distinct alpha noradrenergic receptors differentiated by binding and physiological relationships. Life Sci 24:79-88 Vandewalle A, Farman N, Bonvalet J-P (1978) Renal handling of sodium in Kyoto- Okamoto rats. Am J Physio1235 :F394-F402 Vatner SF (1974) Effects of hemorrhage on regional blood flow distribution in dogs and primates. J Clin Invest 54:225-235 Vaughan ED, Shemasky JH, Gillenwater JY (1971) Mechanism of acute hemodynamic response to ureteral occlusion. Invest Urology 9:109-118 Waickman LA, Abboud FM (1980) Circumflex coronary occlusion inhibits the compensatory increase in sympathetic activity during arterial hypotension. Clin Res 28:717A Walker JL, Thames MD, Abboud FM, Mark AL, Klopfenstein HS (1978) Preferential distribution of inhibitory cardiac receptors in left ventricle of the dog. Am J Physiol 235 :H188-H192 Wasserman K, Huss R, Kullmann R (1980) Dopamine-induced diuresis in the cat without changes in renal hemodynamics. Naunyn-Schmiedebergs Arch Pharmacol 312: 77-83 Watanabe AM, Judy WV, Cardon PV (1974) Effect of L-dopa on blood pressure and sympathetic nerve activity after decarboxylase inhibition in cats. J Pharmacol Exp Ther 188:107-113 Waugh WM (1970) Evidence that renal sympathetic tone modulates the degree of natriuresis upon volume expansion. Fed Proc 29:459 Weaver LC (1977) Cardiopulmonary sympathetic afferent influences on renal nerve activity. Am J Physiol 233 :H592-H599 Weaver LC, Reimann KA (1979) Comparison of sympathetic and vagal cardiac afferent influences on renal nerves. Fed Proc 38:1201 180 G.F. DiBona

Weaver LC, Macklem LJ, Reimann KA, Mickler RL, Oehl RS (1979) Organization of thoracic sympathetic afferent influences on renal nerve activity. Am J Phyiol 237 : H44-H50 Weaver LC, Danos LM, Oehl RS, Meckler RL (1981) Contrasting reflex influences of cardiac afferent nerves during coronary occlusion. Am J Physiol 240:H620-H629 Webb RL, Knuepfer MM, Brody MJ (1981) Central projections of afferent renal nerves. Fed Proc 40:545 Weidinger H, Kirchner F (1967) Sympathische Aktionspotentiale bei nicht narkotisier- ten frei beweglichen Katzen. Pfluegers Arch 294:R23 Weitsen HA, NorveU JE (1969) Cholinergic innervation of the autotransplanted canine kidney. Circ Res 251:535-541 Wennergren G, Henriksson B-A, Weiss L-G, Oberg B (1976) Effects of stimulation of nonmodulated cardiac afferents on renal water and sodium excretion. Acta Physiol Scand 97:261-263 Westfall TC (1977) Local regulation of adrenergic neurotransmission. Physiol Rev 57: 659-728 Westfall TC (1980) Neuroeffector mechanisms. Annu Rev Physiol 42:383-397 Wehlan T J, McCoord AB, Schilling JA (1952) Experimental ascites: the influence of transplantation of the kidneys to the neck. Surg Forum 4:510-516 Whitwam JG, Kidd C, Fussey IV (1979) Responses in sympathetic nerves of the dog evoked by stimulation of somatic nerves. Brain Res 165:219-233 Wilcox CS, Aminoff MJ, Slater JDH (1977) Sodium homeostasis in patients with autonomic failure. Clin Sci 53:321-328 Williams RL, Maines JE, Pearson JE (1971) Direct and systemic effects of guanethidine on renal function. J Pharmacol Exp Ther 177:69-77 Williamson HE, Marchand GR, Bourland WA, Farley DB, Van Orden DE (1976) Ethacrynic acid induced release of prostaglandin E to increase rena blood flow. Prostaglandins 11:519-522 Willis LR, Lappe RW, Hendry DP, Evan AP, Terzian AR (1980) Urinary excretion of radiolabelled norepinephrine after release from renal sympathetic nerves. Life Sci 27:2541-2546 Wilson DR (1980) Pathophysiology of obstructive nephropathy. Kidney Int 16:281 - 292 Wilson DR, Honrath U (1981) Effect of renal denervation, furosemide, and acute saline loading on postobstructive diuresis in the rat. Can J Physiol Pharmacol 59: 59-64 Wilson DR, Honrath U, Cusimano M (1979a) Role of renal nerves in altered sodium reabsorption during transient increases in ureteral pressure. Clin Res 27:433A Wilson DR, Honath U, Sole M (1979b) Effect of acute and chronic denervation on renal function after release of unilateral ureteral obstruction in the rat. Can J Physiol Pharmacol 57:731-737 Winaver J, Chaimovitz C, Better OS (1978) Natrinretic effect of propranolol on dogs with chronic bile duct ligation. Clin Sci 54:603-607 Winternitz SR, Katholi RE, Oparil S (1980) Role of the renal sympathetic nerves in the development and maintenance of hypertension in the spontaneously hypertensive rat. J Clin Invest 66:971-978 Winternitz SR, Oparil S, Katholi RE (1981) Decrease in hypothalamic catecholamines following renal denervation in one-kidney one-clip Goldblatt hypertensive rats. Clin Res 29:362A Woodcock EA, Funder JW, Johnston CI (1978) Decreased cardiac beta adrenoceptor in hypertensive rats. Clin Exp Pharmacol Physiol 5:545-550 Young WS, Kuhar MJ (1980) Alpha-2 adrenergic receptors are associated with renal proximal tubules. Eur J Pharmacol 67:493-495 Yun J, Kelly GM, Bartter FC, Smith H (1977) Role of prostaglandins in the control of renin secretion. Circ Res 40:459-464 The Functions of the Renal Nerves 181

Zambraski E J, DiBona GF (1976) Role of angiotensin II in the antinatriuresis of low level renal nerve stimulation. Am J Physiol 231 : 1105-1110 Zambraski E J, DiBona GF (1979) Interaction of adrenergic stimuli, prostaglandins and angiotensin II in the dog kidney. Proc Soc Exp Biol Med 162:105-111 Zambraski E J, Dunn MJ (1980) Prostaglandins and renal function in chronic bile duct ligated dogs. Proc Am Soc Nephrol 13:111A Zambraski EJ, DiBona GF, Kaloyanides GJ (1976a) Specificity of neural effect on renal tubular sodium reabsorption. Proc Soc Exp Biol Med 151:543-546 Zambraski E J, DiBona GF, Kaloyanides GJ (1976b) Effect of sympathetic blocking agents on the antinatriuresis of reflex renal nerve stimulation. J Pharmacol Exp Ther 198:464-472 Zambraski E J, Prosnitz EH, DiBona GF (1978) Lack of evidence for renal vasodilatation in anesthetized dogs. Proc Soc Exp Biol Med 158:462-465 Zimmerman BG (1978) Actions of angiotensin on adrenergic nerve endings. Fed Proc 37:199-202 Zimmerman H, Ganong WF (1980) Pharmacological evidence that stimulation of central seratonergic pathways increases renin secretion. Neuroendocrinology 30: 101-107 Zimmerman H-D (1972) Elektronenmikroskopische Befunde zur Innervation des Nephron nach Untersuchungen an der fetalen Nachniere des Menschen. Z Zellforsch 129:65-75 Zimmermann H-D (1975) Myelinated nerve fibers in the rat kidney. Cell Tissue Res 160:485-493 Zucker IH, Gilmore JP (1975) Responsiveness of type B atrial receptors in the monkey. Brain Res 95 : 159-165 Zucker IH, Lang M, Hackley JF (1981) Modulation of renal sympathetic nerve activity in the anesthetized dog. Fed Proc 40:522 Author Index

Page numbers in italics refer to the b~liography

Aars H 95, 157, 157 Anderson R J, Henrieh WL, Ayus JC, see Humphreys MH Aars H, Akre S 87, 96, 148, Erickson AL, Gross P 123, 151,167, 168 157 158 Azer M, Gannon R, Kaloyani- Abboud FM, see Thames MD Anderson RJ, see Henrich WL des GJ 112, 117, 158 89, 91,100, 105,145, 178 143,167 Abboud FM, see Waickman Andreucci VE, Canto A Dal, Baer PG, see Diz DI 152, LA 91, 179 Corradi A, Migone L 101, 163 Abboud FM, see Walker JL 158 Baig H, see Pagani M 57, 100, 179 Andreucei VE, Canto A Dal, 72 Abe K, Sato M, Haruyama T, Corradi A, Stanziate R, Bainbridge FA 53, 56 Sato K 143, 158 Migone L 101,158 Baines AD 157 Ablad B, see Caxlsson E 82, Anggard E, see Davila D Baines AD, Chan W 84, 161 106, 143, 162 158 Ablad B, seeKopp U 116, Anggard E, see Larsson C Baines AD, Craan A, Chan W, 138, 139, 144, 145, 146, 142, 171 Morgunov N 83,158 170 Annat G, see Grandjean B Baines A, Morgunov N 83, Abrams HL, see Hollenberg 136, 166 84, 131,158 NK 103, 155, 167 Antonio A, see Neto FR Baines AD, see Carrara MC Adam WR 82, 158 56, 71 109,161 Adams DF, see Hollenberg NK Aoki S, see Takeuchi J 99, Baines AD, see Morgunov N 103, 155, 167 178 84, 85, 172 Adgey AA, see Webb SW 64, Arai S, see Nomura G 108, Baines AD, see Stephenson RK 74 109, 173 84, 177 Adkinson JT, see Szalay L Arendhorst WJ, Beierwaltes Baker DG, Coleridge HM, 114,178 WH 154, 158 Coleridge JCG, Nerdrum T Adrian ED, Bronk DW, Armour JA 16, 18, 66 29, 32, 34,35, 56, 66 Phillips G 87, 158 Arruda JAL, Sabatini S Baker DG, see Kaufman ~fP Aguilera AJ 157 134, 158 56, 69 Aguilera AJ, see Di Bona GF Astrom A, Crafford J 96, Ball SG, see Oates NS 84, 118, 163 158 173 Aguilera AJ, see Stick GL Asztalos B, see Bencsath P Banks R, see Pagani M 47, 117, 118, 176 109,159 49, 50, 60, 72 Akre S, see Aars H 87, 96, Atlas D, Melamed E, Lahar M Banks RO, see MuUinsMM 148, 157 81,158 154, 172 Albert K, see Kottra G 93, Aukland K 99, 101,157, Banzett RB, see Coleridge HM 171 158 20, 29, 36, 40, 67 Alexander EA, see Blendis LM Auld RB, see Blendis LM Barajas L 80, 108, 157, 158, 120, 160 120, 160 159 Alexander RS 46, 66 Aurell M, see Kopp U 116, Barajas L, Silverman AJ, Alexander RW, Gill JR, 138, 139, 144, 145, 146, Muller J 78, 99,159 Yamabe H, Lovenberg W, 170 Barajas L, Wang P 78, 79, Keiser HR 84, 158 Aviado DM, Schmidt CF 64, 81, 159 Aminoff MJ, see Wilcox CS 66 Barajas L, Wang P, Desantis S 111, 180 Aviado DM, see Taquini AC 77, 78, 99, 159 Ammons WS, Santiesteban 44, 73 Baraz LA, see Khayutin VM HL, Kozama S, Manning JW Ayus JC, Stanton CJ, Eneas 34, 62, 69 136,158 JF, Humphreys MH 151,138 Bard P 58, 66 184 Author Index

Barger AC, Liebowitz MR, Bencsath P, Bonvalet J-P, Bishop VS, Lombardi F, Muldowney FP 109, 112, Rouffignac C De 108, Malliani A, Pagani M, Recor- 117, 119, 122, 159 159 datiG 52, 53, 54, 66 Barger AC, see Fray JCS Bencsath P, Szalay L, Bishop VS, Peterson DF 5 8, 85, 164 Demeezky L, Takacs L 66 Barger AC, see Johnson MD 108,159 Bishop VS, see Horwitz LD 120, 121,140, 144, 168 Bencsath P, see Szalay L 54, 69 Barger AC, see Pomeranz BH 114, 177 Bishop VS, see Malliani A 103, 174 Benesath P, see Szenasi G 50, 64, 71 Barger AC, see Rocchini AP 114, 178 Bishop VS, see Mursch DA 85, 136, 175 Bencsath P, see Takacs L 136, 172 Barger AC, see Stinson JM 108, 109, 113, 178 Bishop VS, see Pagani M 72 99, 177 Ben-David E, see Gavendo S Bishop VS, see Peterson DF Barnes AB, see Stinson JM 82, 165 57,72 99, 177 Ben-Ishay D, Knudsen KD, Bishop VS, see Recordati G BartoreUi C, see Guazzi M DahlLK 155,159 23, 72 64, 68 Bennett ED, Brooks NH, Blackshear JL, Spielman WS, Bartter FC, see Gill JR Jr Keddie J, Lis Y, Wilson A Knox FG, Romero JC 110, 112, 165 131,160 143, 160 Bartter FC, see Yun J 143, Bennett ED, Brooks NH, Blair ML 140, 160 180 Lis Y, Wilson A 131, BlakeWD 108, 160 Basilio RD, see Caceiaguida 160 Blantz RC 101, 160 RJ 109, 161 Bennett ED, Keddie J 131, Blantz RC, Konnen KS, Baum T, Shropshire AT 95, 159 Tucker BJ 102, 160 96, 159 Berecek KH, Shaffer RA, Blantz RC, see Steiner RW Beaeham WS, Kunze DL Brody MJ 153, 160 102,.177 46, 66, 96, 149, 159 Bergamaschi M, Longoni AM Blantz RC, see Tucker BJ Beacham WS, Perl ER 46, 58, 66 102, 179 66 Bergamasehi M, see Malliani A Blaschko H 4 Beccari E 18, 66 54, 59, 60, 71 Blaschko H, Burn JH, Carter Behrenbeck DW, see Rein- Bergamaschi M, see Pagani M CW 9 hardt H-W 84, 175 54, 55, 56, 59, 60, 72 Blasingham MC, Shade RE, Beierwaltes WH, Sehryver S, Berkley HJ 14, 66 Share L, Nasjletti A 106, Olson PS, Romerao JC Berl T, Henrich WL, Erickson 160 144, 159 AL, Schrier RW 144,160 Blaufox MD, Lewis EJ, Jagger Beierwaltes WH, see Arend- Bed T, see Henrich WL 143, P, Lauler D, Hickler R, horstWJ 154, 158 144, 167 MerrillJP 111,112, 160 Belcher M, see Felder R Bernard C 107, 160 Blendis LM, Auld RB, Alexan- 82, 164 BerneRM 103,108,160 der EA, Levinsky NG 120, Bell C, Lang WJ 102, 159 Berns AS, see Henrichs WL 160 Bell C, Lang WJ, Laska F 143, 167 Block MA, Wakim KG, Mann 103,159 Berthelsen S, Pettinger WA FC 116,160 Bello-Reuss E 132, 159 105,160 Bloxham DD, see Goetz KL Bello-Reuss E, Colindres RE, Berti G, see Ferrario CM 124, 125, 130, 165 Pastoriza-Munoz E, Mueller 93, 96, 164 Bodart H, see Friggi A 95, R.A, Gottschalk CW 108, Besarab A, Silva P, Landsberg 164 159 L, Epstein FH 131,160 Boettcher DH, see Vatner SF Beilo-Reuss E, Pastoriza- Besch HR Jr, see Judy WV 58,74 Munoz E, Colindres RE 87,168 Bond GC, Lightfoot B 137, 108, 159 Better OS, Massry SG 113, 160 Bello-Reuss E, Trevino DL, 160 Bond GC, see Ehrhart IC 106, Gottschalk CW 118, 120, Better OS, see Winaver J 163" 159 113,180 Bond GC, see FeweU JE 137, Bello-Reuss E, see Higashi Y Bevan JA 105,160 164 134, 167 Bezold A yon, Hirt L 56, Bond GC, see Goetz KL 124, Benchetrit G, Eteradossi J, 63, 74 125, 128, 130, 165 Lemaxchands H 110, 159 Billingsley PR, see Ranson SW Bonjour J-P, Churchill PC, BencsathP 157, 159 13, 14, 16, 72 Malvin RL 108, 160 Bencsath P, Asztalos B, Birteh AG, see Pometanz BH Bonvalet J-P, see Bencsath P Szalay L, Takacs L 109,159 103, 174 108, 159 Author Index 185

Bonvalet J-P, see Vandewalle Brody MJ, see Knuepfer MM Burn I, see Burn JH 9 A 154,179 98,170 Burn HJ 1-8,8-10 Boock E, see Trevan JW 8 Brody MJ, see Mahoney LT Burn JH, BiilbringE 3, 9 Bosnjak ZJ, see Kampine JP 148,171 Burn JH, Dale HH 2, 8 91,169 Brody MJ, see Takeshita A Burn JH, Gibbons WH 10 Bosnjak ZK, Zuperku EJ, 155,178 Burn JH, Hutcheon De, Parker Coon RJ, Kampine JP 32, Brody MJ, see Touw KB RHO 9 66 153,179 Burn JH, Kottegoda SR 9 Botar J 15,66 Brody MJ, see Webb RL Bum JH, Langeman H, Parker Boucher R, see Schiffrin EL 149,180 RHO 9 146,176 Bronk DW, Ferguson LK, Burn JH, Leach EH, Rand MJ, Bouckaert J J, see Heymans C Margaria R, Solandt DY Thompson JW 5,10 45, 46, 69 43, 66 Burn JH, Ng KKF 10 Bourland WA, see Williamson Bronk DW, see Adrian ED Burn JH, Philpot, Trendelen- HE 180 87,158 burg 5 Bourne A, Burn JH 8,9 Brooks CM 45,66 Burn JH, Rand MJ 5, 6, 10, Boykin J, Cadnapaphomchal Brooks NH, see Bennett ED 79,161 P, Burke T, McDonald KM, 131,160 Burn JH, Robinson J 9 Schrier RW 129,160 Brosnihan KG, Szilagyi JE, Burn JH, Tainter ML 9 Brabson JH, see Graham RM Masaki Z, Ferrario CM Burn JH, Trendelenburg U 81,166 93,161 10 Bradley T, see Kopp U 86, Brown AM 16, 19, 32, 34, Burn JH, Truelove LH, Burn I 170 42, 66, 85,161 9 Brady JV, see Randall DC Brown AM, Malliani A 16, Burn JH, Vaughan Williams 58, 72 31, 33, 35, 36, 47, 66 EM, Walker JM 10 Brandstrom A, see Carlsson E Brown AM, see Malliani A Burn JH, see Blaschko H 9 82,161 33, 35, 40, 47, 50, 64, 70, Burn JH, see Bourne A 8,9 Brasil JCF, see Nero FR 56, 71 Burn JH, see BiilbringE 3, 4, 71 Brown AM, see Peterson DF 9 Braumwald E, see Epstein SE 50, 63, 72 Burn JH, see Fleckenstein A 109,163 Brown AM, see Recordati G 5,9 Braun C, see Guzman F 35, 32, 57, 72 Burn JH, see Holland WC 10 57, 68 Brown AM, see Schwartz PJ Burn JH, see Kordik P 9 Braunwald E, see Pagani M 49, 56, 64, 65, 73 Burn JH, see Trevan JW 8 57, 72 Brown EW, see Bristow JD Burnett JC Jr, see Knox FG Brenner BM, see Iino Y 132, 58, 66 114,170 168 BruneUi C, see Chierchia S Busnardo I, see Golin R 148, Brenner BM, see Myers BD 64, 67 166 101,102,172 Bryan WJ, see Fink GD Bricker NS, Staffon RA, 152, 164 Cacciaguida RJ, Pablo NC, Mahoney EP, Merrill JP BiilbringE 4 Basilio RD, Porush JG 109, 116,161 BiilbringE, Burn JH 3, 4, 161 Bristow JD, Brown EW, 9 Cadnapaphornchal P, see Cunningham DJC 58, 66 BfilbringE, Burn JH, Shelley Boykin J 129,160 Brizzee K, see Richins CA HJ 9 Calaresu FR, Kim P, Nakamura 46, 72 BiilbringE, Burn JH, Skoglund H, Sato A 96,148,161 Brod J, Fejfar Z, Fajfarova CR 9 Calaresu FR, Stella A, Zanchet- MH 112, 161 BiilbringE, see Burn JH 3, 9 tiA 148,161 Brody M 99, 157,161 BiilbringE, see Kordik P 9 Calaresu FR, see Ciriello J 97, Brody MJ, Fink GD, Buggy Buggy J, see Brody MJ 148, 162 J, Haywood JR, Gordon FJ, 161 Caleagno P, see Felder R 82, Knuepfer M, Mow M, Maho- Buggy J, see Fink GD 148, 164 ney L, JohnsonAK 148, 164 Caliguiri L, see Randall WC 161 Burch GE, Pasquale NP De 43, 72 Brody MJ, Johnson AK 148, 35,67 Campbell WB, Graham RM, 153,161 Burger BM, see HoUenberg Jackson EK 139, 144,161 Brody MJ, see Berecek KH NK 155,167 Campbell WB, Zimmer JA 153,160 Burgess PR, Perl ER 17, 22, 144,161 Brody MJ, see Fink GD 148, 26, 33, 34, 43, 67 Campbell WB, see Keeton TK 152, 155,164 Burke T, see Boykin J 129,160 135,169 186 Authorlndex

Cannon PJ, see Oliver JA 86, Chapman LW, Mittman U, Coleridge HM, see Kaufman MP 106, 143,173 Meehan JP 128,162 56, 69 Cant JR, Vander AJ 120,161 Chapman LW, see Hiatt N Coleridge JCG, Coleridge HM Cant JR, see Rocehini AP 85, 151,167 57,67 175 Charuzi Y, see Figueras Coleridge JCG, Hemingway A, Canto A Dal, see Andreucci VE 64, 68 Holmes RL, Linden RJ 17, 101,158 Chasis H, see Smith HW 20, 6 7 Cardinal J, see Carriere S 161 101,177 Coleridge JCG, see Baker DG Cardon PV, see Watanabe AM Chatel R De 122,162 29, 32, 34, 35, 56, 66 95,179 Chenitz WR, see Hollen- Coleridge JCG, see Coleridge Caretero OA, Scicli AG 147, berg NK 155,167 HM 32, 35, 36, 40, 42, 56, 161 Chernilovskaya PE, see 61, 62, 67, 87, 91, 92, 99, Carlson DE, Schramm LP 105, Khayutin VM 34, 62, 162 161 69 Coleridge JCG, see Kaufman Carlson DE, see Schramm LP Chevalier-Cholat A-M, see MP 56, 69 105,176 Friggi A 95,164 Colindres RE, Spielman WS, Carlsson E, Ablad B, Brand- Chierchia S, Brunelli C, Moss NG, Harrington WW, strom A, Carlsson B 82, Simonetti I, Lazzari M, Gottschalk CW 150,162 161 Maseri A 64,67 Colindres RE, see BeUo-Reuss Carlsson B, see Carlsson E Childers J, see Schneider E E 108,159 82, 161 110,176 Colindres RE, see Szalay L Carpenter D, Engberg I, Lund- Chirnoskey JE, see Stinson 114,178 bergA 45, 67 JM 99,177 Concha J, Norris B 99, Cart AA, see Fill JR Jr 112, Churchill PC, see Bonjour 162 165 J-P 108,160 Consolo S, Garattini S, Carrara MC, Baines AD 109, Cinca J, see Figueras J 64, Ladinsky H, Thoenen H 6 161 68 Cooke M, see Felder R 82, Carriere S, Cardinal J, Grim- Ciriello J, Calaresu FR 97, 164 mellec CL Le 161 162 Coon RI, see Kampine JP Carson RP, see Lazzara R CirieUo J, see Kline RL 91,169 130,171 152, 153,170 Coon RL, see Bosnjak ZK Carter CW, see Blaschko H 9 Clement DL, Pelletier CL, 32, 66 Casalone C, see Lombardi F Shepherd JT 85, 89, 90, Coon RL, see Hess GL 23, 45, 70 93,162 24, 69 Casati R, Lombardi F, MaUiani Click RL, Joyner WL, Gil- Coon RL, see Kostreva DR A 16, 18, 25, 26, 27, 28, 29, more JP 101,162 22, 69 31, 32, 34, 35, 67 Cobu~n JW, see Chaimovitz C Coote JH, Hilton SM, Perez- Casati R, see Lombardi F 16, 113,161 Gonzales JF 58,67 25, 31, 32, 33, 35, 56, 70 Coggeshall RE 17,67 Coote JH, MacLeod VH Casper AGT, see Gill JR Jr CoggeshaU RE, Coulter JD, 96,162 109, 112, 120, 121,165 WillisWD 17,67 Corbett JL, Frankel HL, Castanet A, see Kostreva DR CoggeshaU RE, Galbraith SL Harris PJ 61, 67 95,100, 150,170 14,67 Cornish KG, GiLmore JP CattonWT 19, 67 Colditz JH yon, see Purtock RV 130,162 Ceasar PM, see Reynolds GP 51, 72,90, 101,174 Cornish KG, see Gilmore JP 85,175 Coleman TG, see Hall JE 167 101,165 Cerati D, see Recordati G 151, Coleridge CG, Linden RJ 54, Corradi A, see Andreucci VE 175 67 101,158 Chabardes D, see Morel F Coleridge HM, Coleridge JCG Costantin LR 63,67 131,172 32, 35, 67, 87, 91, 92, 99, Coulter JD, see Coggeshall Chaimovitz C, Massry SG, 162 RE 17, 67 Friedler RM, Coburn JW Coleridge HM, Coleridge JCG, Cowan J, see Randall WC 113,161 Kidd C 20, 29, 40, 42, 56, 43, 72 Chaimovitz C, see Winaver J 61,62,67 Cowley AW, see Hall JE 166, 113,180 Coleridge HM, Kidd C, Coleridge 167 Chan CC, see Kalsner S 142, JCG, Banzett RB 20, 29, 36, Craan A, see Baines AD 83, 169 40, 67 158 Chan W, see Baines AD 83, Coleridge HM, see Baker DG Crafford J, see Astrom A 96, 84,158 29, 32, 34, 35, 56, 66 158 ChanYL 132,161 Coleridge HM, see Coleridge Cross CE, see Salisbury PF Chang and Rand 6 JCG 20, 29, 57, 67 64, 73 Author Index 189

Gandler T, see Graham RM Gill JR Jr 76,165 Golin R, see Stella A 136, 81,166 Gill JR Jr, Bartter FC 110, 177 Gandler T, see Pettinger W 165 Gomer SK, Zimmerman BG 82,174 Gill JR Jr, Cart AA, Fleisch- 99,166 Gannon R, see Azer M 112, mann LE, Casper AGT, Gomez DM 101,166 117,158 Bartter FC 112,165 Gordon D, Peart WS, Wilcox Ganong WF, see Reid IA Gill JR Jr, Casper AGT CS 110,166 135,175 109, 120, 121,165 Gordon F J, see Brody MJ Ganong WF, see Zimmerman Gill JR, see Alexander RW 148,161 H 137,181 84,158 Gorgas K 80,157,166 Ganz W, see Figueras J 64, Gilmore JP 124,165 Gottschalk CW 76, 157, 68 Gilmore JP, Cornish KG, 166 Garattini S, see Consolo S Rogers SD, Joyner WL Gottschalk CW, see Bello- 6 101,165 Reuss E 108, 118,120, Garcia R, see Schiffrin EL Gilmore JP, Zucker IH 159 146, 176 124,130,165 Gottschalk CW, see Colindres Gaskell WH 14, 68 Gilmore JP, see Click RL RE 150,162 Gates HO, see Stinson JM 101,162 Gottschalk WC, see Rogenes 100, 177 Gilmore JP, see Cornish KG PR 110,176 Gatzka M, see Kaczmarczyk G 130, 162 Gottschalk CW, see Szalay L 103,168 Gilmore JP, see Echtenkamp 114,178 Gauer OH, Henry JP 124, SF 89, 90,163 Graham RM, Brabson JH, 165 Gilmore JP, see Zucker IH Stephenson WH, Pettinger Gavendo S, Kapuler S, Serban 130, 181 WA 81,166 I, Iania I, Ben-David E, Gillenwater JY, see Vaughan Grahem RM, Sagalowsky AI, Eliahou H 82,165 ED 149,179 Pettinger WA, Murphy T, Gavendo S, see Eliahou HE Ginsburg JM, see Ehrhart IC Gandler T, Sanford SE 82,163 106,163 81,166 Gazdar A 111,165 Gleason S, see Schneider E Graham RM, see Campbell WB Gazdar AF, Dammin GF 110,176 139,144,161 111,165 Goetz KL 130,165 Grandjean B, Annat G, Gebber GL 96,165 Goetz KL, Bond GC 128, Vincent M, Sassard J 136, Gebber GL, see McCall RB 165 166 172 Goetz KL, Bond GC, Bloxham Grange RG La, Mitchell SW Gebhart GF, see Knuepfer MM DD 124,125,130,165 129,171 98,170 Goetz KL, Wang BC, Grange RG La, Sloop CH, Geer PG, see Goetz KL Hakumaki MOK, Fater DC, Schmid HE 117, 135, 171 129,165 Geer PG, Sundet WD 129, Greven J, Klein H 134, Geller E, see Kezdi P 87, 165 166 103,169 Goetz KL, see Fater DC Grignolo A, Koepke JP, Gellert R, see Kurkus J 109, 130, 163 Obrist PA 131,166 171 Goetz KL, see Schultz HD Grignolo A, see Koepke JP Gellert R, see Sadowski J 130,176 131,170 103,110,114,176 Goldberg LI 102,166 Grimmellec CL Le, see Genest J, see Schiffrin EL Goldherg LI, Kohli JD 102, Carriere S 161 146, 176 166 Grix ALe, see Hillemand B Genovesi S, see Recordati G Goldberg LI, Volkman PH, 76,167 97,151,175 Kohli JD 102,166 Gross P, see Anderson RJ Gerber JG, Keller RT, Nies AS Goldberg LI, Weder AB 123,158 142.165 133,134,166 Gross R 157 Gerber JG, Olson RD, Nies AS Goldberg LI, see Dinerstein Gross R, Hackenburg H-M, 144,165 RJ 82, 103,163 Hackenthal E, Kirehheim H Gerber JG, see Data JL Goldberg M, see Grossman 122, 136,166 143,162 RA 129,166 Gross R, Kirchheim H 87, Gerber JG, see Olson RD Goldring W, see Smith HW 103,136,166 140, 141,143, 1 73 101, 177 Gross R, Ruffman K, Kirch- Gerhart KD, see Foreman RD Go/in R, Busnardo I, Stella A, helm H 103,104, 122, 136, 65, 68 Zanchetti A 148,166 166 Gibbons WH, see Burn JH Golin R, see Dampney RAL Gross R, see Kirehheim HR 10 136,162 87,170 190 Author Index

Grossman RA, Rosing DR, Hattori N, see Nomura G Higashi Y, Bello-Reuss E Szidon JP, Goldberg M 108, 109,173 134,167 129,166 Haven J De, Sherwin R, Hillemand B, Leroy J, Joly Grundfest H 19,61,68 Hendler R, Felig P 85, JP, Grix ALe 76,167 Guazzi M, Polese A, Fiorentini 111,162 Hilton SM 58,69 C, Magrini F, Bartorelli C Hayakawa S, see Himori N Hilton SM, Spyer KM 96, 64, 68 139,167 167 Guazzi M, Polese A, Fiorentini Haywood JR, see Brody MJ Hilton SM, see Coote JH C, Magrini F, Olivari MT, 148,161 58,67 BartorelliC 64,68 Haywood JR, see Fink GD Himori N, Hayakawa S, Gupta PD 53,68 148,164 Ishimori T 139,167 Gupta PD, Singh M 53, 68 Haywood JR, see Mahoney Himori N, Izumi A, Ishimori Gushwa L, see Tucker BJ LT 148,171 T 139,167 102, 179 Haywood JR, see Touw KB Hinke JAM, see Friedman SM Gutkowska J, see Schiffrin 153, 179 155,164 EL 146,176 HeadH 61, 63, 68 Hirasawa K, see Takeuchi J Guttmann L, Whitteridge D Heinbecker P, White HL 95,124, 178 46, 68 126,167 Hirt L, see Bezold Avon Guyton AD, see Hall JE Heindxickx GR, see Vatner SF 56, 63, 74 166, 167 58, 74 Hjemdahl P, see Kopp U Guzman F, Braun C, Lim RKS Hemingway A, see Coleridge 86, 170 35, 57, 68 JCG 17,20,67 Hockel GM, see Judy WV Guzzetti S, see Pagani M Henderson RC, see Dinerstein 168 54, 56, 57, 59, 72 RJ 82, 103,163 Hoffman BB, Lefkowitz RJ Hendler R, see Haven J De 82,167 Hackenburg H-M, see Gross R 85,111,162 Hoffmann PC, see Dinerstein 122,136,166 Henrich WL, Anderson RJ, RJ 82,103,163 Hackenthal E, see Gross R Berns AS, McDonald KM, Holdaas H 157, 122, 136,166 Paulsen PJ, Berl T, Schrier Holdaas H, Di Bona GF Hackley JF, see Zucker IH RW 143,167 137,138,167 90,181 Henrich WL, Schrier RW, Holdaas H, Di Bona GF, Hainsworth R, Kidd C, Linden BerlT 144,167 KiilF 147,167 RJ 11,68 Henrich WL, see Anderson RJ Holland WC, Burn JH 10 Hakumaki MOK, see Goetz KL 123,158 Hollenbexg NK, Adams DF, 129,165 Henrich WL, see Berl T Rashid A, Epstein M, Hail DA, see Polhemus RE 144,160 Abrams HL, Merrill JP 132,174 Henriksson B-A, see 103,167 Hall JE, Guyton AD, Cowley Wennergren G 130,180 Hollenberg NK, Adams DF, Solomon H, Chenitz WR, AW 166 Henry DP, see Judy WV Hall JE, Guyton AC, Jackson 87,168 Burger BM, Abrams HL, TE, Coleman TG, Lohmeier Henry DP, see Lappe RW Merrill JP 155,167 TE, Trippodo NC 167 84, 86,171 . Hollifield JW, see Data JR Hanada S, see Takeuchi J Hendry DP, see Willis LR 143,162 Hollifield JW, see Frolich JC 77, 87, 99, 178 84,180 Hanson R, see Schneider E Henry JP, see Gauer OH 143,164 110,176 124,165 Hollingsead P, Willis LR Hardwick DF, see Friedman Hermansson K, Larson M, 132,167 SM 155,164 Kallskog O, Wolgast M Holmes R 15,69 Harley A, see Effendigil MC 119,167 Holmes R, Torrance RW 131,163 Hess GL, Zuperku EJ, Coon 17, 19, 40, 69 Harrington WW, see Colindres RL, Kampine JP 23, 24 Holmes RL 15, 69 RE 150,162 69 Holmes RL, see Coleridge Harrington WW, see iiMoss Heymans C, Bouckaert J J, JCG 17,20,67 NG 115,151,172 Farber S, Hsu FY 45, 46 Honig A 123,167 Harris PJ, see Corbett JL 69 Honig A, Schmidt A 123, 61,67 Heymans C, Neil E 13,69 167 Honig A, Schmidt M, Freyse Haruyama T, see Abe K Hiatt N, Chapman LW, David- EJ 123,167 143,158 sonMB 151,167 Hasson DM, see Randall DC Hickler R, see Blaufox MD Honour J, see Littler WA 58, 72 111,112,160 64, 70 Author Index 187

Crowshaw K, see McGriff JC Di Bona GF, Johns EJ, Os- Dunn MJ, Liard JF, Dray F 106, 141,172 born JL 123,136,163 142, 163 CrumpWL, see Data JL 143, Di Bona GF, Osborn JL Dunn MJ, see Zambraski EJ 162 133,162 107, 181 Cunningham DJC, see Bristow Di Bona GF, Rios LL 115, Dusting GF, see Staszewska- JD 58, 66 116, 150, 154,163 Barzak 2 63, 73 Cusik JF, see Seagard JL 14, Di Bona GF, Sawin LL 111, 73 112,163 Early LE, see Reid IA 140, Cusimano M, see Wilson DR Di Bona GF, Zambraski EJ, 175 113,180 Aguilera AJ, Kaloyanides GJ Echt M, see Kaczmarczyk G Cyon E, Ludwig C 63, 67 118,163 129,168 Di Bona GF, see Francisco LL Echtenkamp SF, Gilmore JP Dale LK, see Ben-Ishay D 97, 143,148, 149, 153,154, 90, 163 155, 159 164 Echtenkamp SF, Zueker IH, Dale HH, see Burn JH 2, 8 Di Bona GF, see Holdaas H Gilmore JP 89, 163 Dammin GF, see Gazdar AF 137,138, 147,167 Edgeworth FH 12, 14, 67 111,165 Di Bona GF, see Osbom JL Effendigil MC, Harley A, Dampney RAL, Stella A, 135,138, 139, 141,142, Deegan T, McKendrick CS Golin R, Zanchetti A 136, 147,174 131,163 162 Di Bona GF, see Prosnitz EII Ehrhart IC, Bond GC, Gins- Dampney RAL, see Stella A 88, 95,100, 103,109, 122, burg JM 106, 163 136,177 124, 127, 128,174 Eigenheer F, see Kaczmarczyk Danos LM, see Weaver LC 45, Di Bona GF, see Rickstein S-E G 103,168 74, 92, 180 87, 93, 94, 153, 154,175 Eilersten E, see Olson U Data JL, Gerber JG, Crump WL Di Bona GF, see Slick GL 106, 174 Frohlich JC, Hollifield JW, 113, 117, 118,176 Eisner G, see Felder R 82, NiesAS 143,162 Di Bona GF, see Thames MD 164 Davidov M, see Mroczek WJ 145, 146, 147,178 Eisner G, see Montgomery 109, 172 Di Bona GF, see Zambraski EJ S 172 Davidson MB, see Hiatt N 151 99, 100, 106,117, 118, 119, Eliahou HE, Gavendo S, 167 121,122, 133, 135,181 Serban I, Kapuler S, Iaina Davfla D, Davila T, Oliw E, Dicintio R, see Recordati G A 82,163 AnggardE 106,143,162 151,175 Eliahou H, see Gavendo S Davila T, see Davila D 106, Dinerstein R J, Vannice J, 82, 165 143,162 Henderson RC, Roth LJ, Eneas JF, see Ayus JC 151, Davis HA, Horton EW 118, Goldberg LI, Hoffmann PC 158 147,162 82, 103,163 Engberg I, Lundberg A, Davis JO, Freeman RH 135, Discala VA, see Kinney MJ RyaU RW 45, 68 162 128,129,169 Engberg I, see Carpenter D Davis JO, see Forrest JM De Diz DI, Nasjletti A, Baer PG 45, 67 143,162 152,163 Engelhorn R 87, 163 Davis TP, see For~est JM De Dogiel AS 14, 36,67 Epstein FH, see Besarab A 143,162 Dokukin AV 63, 67 131,160 Deegan T, see Effendigil MC Donald DE 136,163 Epstein M 124, 163 131,163 Donald DE, Shepherd JT Epstein M, Lifschitz MD Deen WD, see Myers BD 101, 87, 99,135,163 106, 163 102,172 Donald DE, see Jarecki M Epstein M, see Hollenberg NK Della Bella P, see Lombardi F 136,168 103, 167 16, 25, 31-33, 35, 45, 46, Donald DE, see Mancia G 89, Epstein SE, Braumwald E 56,70 104,105,172 109, I63 Demeczky L, see Bencsath P Donald DE, see Powis DA 136, Erickson AL, see Anderson RJ 108,159 140, 174 123, 158 Dequattro V, see Nagatsu T Downman CBB, McSwiney BA Erickson AL, see Berl T 84,172 46, 67 144,160 Desantis S, see Barajas L 77, Dray F, see Dunn MJ 142, Eriksson B-M, see Kopp U 78, 99, 159 163 86,170 Di Bona GF 76, 78, 115,116, Durtham EW, Zimmermann Essen H Van, see Struyker- 162 BG 118, 147,163 Boudier I-IAJ 154, 177 Di Bona GF, Johns EJ 123, Dunlap CL, see Romero JC Estefanous FG, Tarazi RC 65, 133, 136,162 143, 176 68 188 Author Index

Estefanous FG, see Tarazi RC Ferrario, see Takeshita Francisco LL, Hoversten LG, 65, 73 93, Di Bona GF 97,149,164 Eteradossi J, see Benchetrit Ferreira SH, see Staszewska- Francisco LL, Osbom JR, G 110,159 Batzak J 50, 73 DiBonaGF 143,149, Evan AP, see Willis LR 84, Ferris TF, see Stein JH 120, 164 180 1 77 Francisco LL, Sawin LL, Evans MH, see Franz DN FeweU JE, Bond GC 137, Di Bona GF 153,154, 46, 68 164 164 Evenwel R, see Stryuker- Figueras J, Cinca J 64, 68 Frankel HL, see Corbett JR Boudier HAJ 154,177 Figueras J, Singh BN, Ganz W, 61,67 Charuzi Y, Swan HJC Franz DN, Evans MH, Perl Fahri ER, see Johnson MD 64, 68 ER 46, 68 140,144,168 Fink GD, Brody MJ 152,164 Fray JCS 135,164 Fajfarova MH, see Brod J FinkGD, BryanWJ 152, Fray JCS, Johnson MD, 112,161 164 Barger AC 85,164 Farber S, see Heymans C Fink GD, Buggx J, Haywood Freeman RH, see Davis JO 45, 46, 69 JR, Johnson AK, Brody 135,162 Farley DB, see WiUiamson HE MJ 148,164 Freeman RH, see Forrest 180 Fink GD, Takeshita A, Mark A JMDe 143,162 Farman N, see Vandewalle A AL, Broady MJ 155,164 Frenzel S, see Rumpf KW 154, 1 79 Fink GD, see Brody MJ 148, 143,176 Farrell SK, see Judy WV 161 Freyse EJ, see Honig A 153,168 Finnerty FA, see Mroczek WJ 123,167 Fater DC, see Goetz KL 109, 1 72 Friedler RM, see Chaimovitz 129,165 Fiorentini C, see Guazzi M C 113,161 Fater DC, see Schultz HD 64, 68 Friedman JJ, see LLoyd TC 130, 176 Fischer A, see Szalay L 100, 171 Fater FD, Sundet WD, Schultz 114,177 Friedman MI, see Sawchenko HD, Goetz KL 130,163 Fisher SJ, Malvin RL 137, PE 131,176 Fedina L, Katunskii AY, 164 Friedman SM, Hinke JAM, Khayutin VM, Mitsanyi A Fitz A 157, Hardwick DF 155,164 94,164 Fleckenstein A, Burn JH Friggi A, Chevalier-Cholat A-M, Fedina L, Kovach GB, Huszar 5,9 Bodard H 95,164 V 95,164 Fleischmann LE, see Gill Friggi A, Chevalier-eholat A-M, Fejfar Z, see Brod J 112, JR Jr 112,165 TorresaniJ 95,164 161 Flier SR, see Iino Y 132, Frolich JC, Hollifield JW, Felder R, Pelyao J, Belcher M, 168 Wilson JP, Sweetman BJ, Calcagno P, Eisner G, Jose P Flint JF, see Kahl FR 100, Seyberth HW, Oates JA 82, 164 169 143,164 Felder R, Pelyao J, Wargo A, FloydK 15, 68 Frohlich JC, see Data JL Schoelkopf L, Cooke M, Folkow B 157, 143,162 Jose P, Eisner G 82,164 Folkow B, Johannson B, Fujita S, see Ninomiya I Felder R, Sch0elkopf L, Lofving B 104, 164 94,173 Pelazo J, Belche~ M, Fontaine R, see Leriche R Fukiyama K 96,165 Calcagno P, Einer G, Jose P 34, 69 Fuller CA, see Kass DA 125, 82,164 Foreman RD, Ohata CA 169 Felder RB, Thames MD 44, 65, 68 Funder JW, see Woodcock EA 63, 68, 82, 92,164 Foreman RD, Ohata CA, 82,180 Felig P, see Haven J De Gerhart KD 65, 68 Furlan R, see Pagani M 54, 85,111,162 Foreman RD, see Schwartz 56, 57, 59, 72 FellC, see DiSalvo J 99, PJ 64, 73 Fussey IV, see Whitwam JG 163 Forrest JM De, Davis JO, 94,180 Ferguson LK, see Bronk DW Freeman RH, Seymour AA, 43,66 Row BP, Williams GM, Gabrilovich L, see Morczek Fernandez de Molina A, Perl Davis TP 143,162 WJ 109,172 ER 46, 68 Fouda FM, see Tarazi RC Gaddum JH, see Trevan JW 8 Ferrario CM, McCubbin JW, 65,73 Galbraith SL, see Coggeshall Berti G 93, 96,164 Francisco LL 157,164 RE 14, 67 Ferrario CM, see Brosnihan Francisco LL, Di Bona GF Gallaxdo R, Pang PKT, Sawyer KG 93,161 148,164 WH 109,165 Author Index 191

Honrath U, see Wilson DR Jackson R, see Szalay L Judy WV, Watanabe AM, 108,113,180 114,178 Hertry DP, Besch HR Jr, Hope DB 4 Jackson TE, see Hall JE Murphy WR, Hockel GM Horn DL van, see Seagrad JL 167 87,168 14, 73 Jagger P, see Blaufox MD Judy WV, see Watanabe AM Horton EW, see Davis HA 111,112,160 95,179 118, 147,162 James TN, see Wallacli R Julius S, see Kiowski W Horwitz LD, Bishop VS 65, 74 137,169 54, 69 Jarecki M, Thoren PN, Donald Houck CR 116,167 DE 136,168 Kaczmarczyk G, Echt M, Hoversten LG 157, Jarrott B, Louis WJ, Somers Mohnhaupt R, Singer B, Hoversten LG, see Francisco RJ 81,168 Reinhardt HW 129, 168 LL 97,149,164 Johannson B, see Folkow B Kaczmarczyk G, Eigenheer F, Hsu FY, see Heymans C 104,164 Gatzka M, Kuhl U, Reinhardt 45, 46, 69 Johns EJ 102, 139, 157, HW 103,168 Humphreys MH, Ayus JC 168 Kaczmarczyk G, Schimm_rick 151,167 Johns EJ, Lewis BA, Singer B B, Mohnhaupt R, Reinhardt Humphreys MH, Ayus JC 102, 116,168 HW 84,168 Stanton CJ 151,168 Johns EJ, Murdock R, Singer Kaczmaxczyk G, see Humphreys MH, see B 118, 147,168 Reinhardt HW 129, 130 Ayus JC 151,158 Johns EJ, see Di Bona GF 175 Humphreys MH, see 123,133,136,162, 163 Kaczmarczyk G, see Schrier RW 112, 176 Johnson AK, see Brody MJ Simgen B 129, 176 Huss R, see Wasserman K 148,153,161 Kady NN 96,97,149, 133,179 Johnson AK, see Fink GD 168 Huszar V, see Fedina L 148,164 Kahl FR, Flint JF, Szidon FP 95,164 Johnson AK, see Knuepfer 100,169 Hutcheon De, see Burn JH MM 98,170 Kaisaka K, see Ueda H 96, 9 Johnson AK, see Mahoney 148,179 LT 148,171 Kallskog O, see Hermansson Iaina A, see Eliahou HE Johnson MD, Barger AC K 119,167 82,163 120,168 Kaloyanides GJ 157 Iania I, see Gavendo S Johnson MD, Fahri ER, Troen Kaloyanides G J, see Azer M 82,165 BR, BargerAC 140, 144 112, 117, 158 Igler FO, see Purtock RV 168 Kaloyanides GJ, see Di Bona 51, 72, 90, 101,174 Johnson MD, Malvin RL GF 118,163 Iino S, see Takeuchi J 121,168 Kaloyanides GJ, see Slick GL 77, 87, 99, 178 Johnson MD, Shier DN, Barger 113,117, 118,176 Iino Y, Brenner BM 132, AC 121,140,168 Kaloyanides GJ, see 168 Johnson MD, see Fray JCS ZambraskiEJ 117, 119, Iino Y, Flier SR, Brenner BM 85,164 121,122, 133,181 132,168 Johnston BD 15, 69 Kalsner S, ChanCC 142, Imbert-Teboul M, see Morel F Johnston CI, see Woodcock 169 131,172 EA 82,180 Kamisaka K, see Uchida Y Ing HR 4 Joly JP, see Hillemand B 18, 23, 24, 25, 33, 34, 74, Inoue G, see Takeuchi J 76, 16 7 97,179 99,178 Jones JJ 54,69 Kamisaka K, see Ueda H InselP 157, Jonnesco T 34,69 19, 20, 24, 33, 74, 96, Insel PA, Snavely MD 81, Jose P, see Felder R 82, 179 82,168 164 Kampine JH, see Purtock RV Irisawa H, see Ninomiya I Jose P, see Montgomery S 90, 101, 174 94,173 172 Kampine JP, Bosnjak ZJ, Ishimori T, see Himori N Joyner WL, see Click RL Coon RI, Kostreva DR, 139,167 101,162 Seagard JL, Zuperku EJ Izumi A, see Himori N 139, Joyner WL, see Gilmore JP 91, 169 167 101, 165 Kampine JP, see Bosnjak ZK Judy WV, Farrell SK 153, 32, 66 Jackson CG, see Stinson JM 168 Kampine JP, see Hess GL 100, 177 Judy WV, Thompson JR, 23, 24, 69 Jackson EK, see Campbell WB Wilson MF 87, 93, Kampine JP, see Kostreva DR 139,144,161 168 22, 69, 95,100,150,1 70 192 Author Index

Kampine JP, see Purtock RV Kellgren JH, see Lewis T Kline RL, Ciriello J, Mercer 51,72 12,69 PF 152~ 153~170 Kampine JP, see Seagard JL Kelly GM, see Yun J 143, Kline RL, Kelton PM, Mercer 14,73 180 PF 152,170 Kaplan SA, Rapaport S Kelton PM, see Kline RL Kline RL, Mercer PF 115,153, 108, • 69 152,170 170 Kappagoda CT 124,125, Kendrick E, Oberg B, Kline RL, Stuart PJ, Mercer 169 Wennergren G 105,169 PF 115,153,170 Kappagoda CT, Knapp MF, Kerkhof P, see Pagani M Klopfenstein HS, see Thames Linden R J, Pearson MJ, 72 MD 100,178 Whitaker EM 126,169 Kezdi P, Geller E 87,103, Klopfenstein HS, see Walker Kappagoda CT, Linden R J, 169 JL 100,179 Snow HM 129,169 Khabarova AY 15,69 Knapp MF, Linden RJ, Kappagoda CT, Linden RJ, Khayutin VM, Baraz LA, Mary DASG, Pearson MJ Snow HM, Whitaker EM Lukoshkova EV, Sonina 127,170 126,169 RS, Chernilovskaya PE Knapp MF, see Kappagoda Kappagoda CT, Linden RJ, 34,62,69 CT 126,169 SreeharanN 128,169 Khayutin VM, see Fedina L Knox FG, Burnett JC Jr, Kappagoda CT, see Karim F 94,164 Kohan DE, Spielman WS, 100,169 Kibe Y, see Nomura G 108, Strand JC 114, I70 Kappagoda CT, see Sivanan- 173 Knox FG, see Blackshear JL than N 125, 176 Kidd C, see Coleridge HM 143,160 Kapuler S, see Eliahou HE 20, 29, 36, 40, 42, 56, 61, Knox FG, see Standhoy JW 82, 168 62, 67 109, 177 Kapuler S, see Gavendo S Kidd C, see Hainsworth R Knudsen KD, see Ben-Ishay 82, 165 11,68 D 155,159 Karim F, Kappagoda CT Kidd C, see Karim F 88, Knuepfer MM, Mohrland JS, 100,169 100,103,124,169 Shaffer RA, Gebhart GF, Karim F, Kidd C, Malpus CM, Kidd C, see Whitwam JG Johnson AK, Brody MJ PennaPE 88,100,103, 94,180 98,170 124, 169 Kiil F 157 Knuepfer M, see Brody MJ Karp RB, see Wallach R Kill F, see Holdaas H 147, 148,161 65,74 167 Knuepfer MM, see Webb RL Kasahara M, see Miller MR Kirn JK, Linas SL, Schrier RW 149,180 15, 71 76,169 Koepchen HP 157 Kaspar RL, see Peterson DF Kirn P, see Colaresu FR Koepke JP, Grignolo A, 57, 72 96,148,161 Obrist PA 131,170 Kass DA, Sulzman FM, Fuller Kinney MJ, Stein RM, Discala Koepke JP, see Grignolo A CA, Moore-Ede MC 125, VA 128, 129,169 131,166 169 Kiowski W, Julius S 137, Kohan DE, see Knox FG Katholi RE, Naftilan AJ, 169 114, 170 Oparil S 152, 153,169 Kirchheim H 99,157, 170 Kohli JD, see Goldberg LI Katholi RE, see Winternitz Kirchheim HR, Gross R 102,166 SR 152, 180 87, 170 Konnen KS, see Blantz RC Katholi RE, Winternitz SR, Kirchheim H, see Gross R 102,160 Oparil S 152,169 87,103,104,122,136, KoppU 135,157,170 Katunskii AY, see Fedina L 166 Kopp U, Aurell M, Nilsson 94,164 KLrchner F, see Weidinger H IM, Ablad B 116,138, Katz MA, Shear L 116, 87,180 144, 170 169 Kishimoto T, see Ueda J Kopp U, Hjemdahl P, Eriksson Kaufman MP, Baker DG, 99,179 B-M, Bradley T 86, 1 70 Coleridge HM, Coleridge Kitamura K, see Takeuchi J Kopp U, Aurell M, JCG 56, 69 77,87,99,178 Sjolander M, Ablad B Keddie J, see Bennett ED Klain GF, see Lazzara R 145,146, 170 131, 159, 160 130,171 Kopp U, Aurell M, Svensson Keeton TK, Campbell WB Kleeman CR, see Klein LA L, Ablad B 139,170 135,169 109, 170 Kordik P, Biilbring E, Burn Keiser HR, see Alexander RW Klein H, see Greven J 134, JH 9 84,158 166 Kostreva DR, Castaver A, Keller RT, see Gerber JG Klein LA, Liberman B, Laks M, Kampine JP 95,100, 142,165 Kleeman CR 109,170 170 Author Index 193

Kostreva DR, Seagard JL, Langeman H, see Burn JH Liard JF, see Dunn MJ 142, Castanet A, Kampine JP 9 163 150,170 Langley JN 12, 13,45,69 Liberman B, see Klein LA Kostreva DR, Zuperku E J, Lappe RW, Hertry DP, Willis 109,170 Purtock RV, Coon LR, LR 84,86,171 Liebowitz MR, see Barger AC Kampine JP 22,69 Lappe RW, see Willis LR 84, 109,112,117,119,122, Kostreva DR, see Kampine JP 180 159 91,169 Larson M, see Hermansson K Lifschitz MD 110, 115, Kostreva DR, see Seagard JL 119,167 171 14, 73 Larsson C, Weber P, AnggaId Lifschitz MD, see Epstein M Kotchen TA, see Leavitt ML E 142,171 106,163 140, 171 Lasher EP, see Rushmer RF Lightfoot B, see Bond GC Kottegoda SR, see Burn JH 58, 73 137,160 9 Laska F, see Bell C 103, Lim RKS, see Guzman F Kottra G, Albert K, Takacs L 159 35, 57, 68 93,171 Lassiter WE, see Szalay L Linas SL, see Kiln JK 76, KottraG, Takacs L 149, 114,178 169 170 Lauler D, see Blaufox MD Linden RJ 53, 69, 76, Kovach GB, see Fedina L 111,112,160 99,171 95,164 LawtonWJ 147,157 Linden RJ, Mary DASG, Kozama S, see Ammons WS Lazzara R, Carson RP, Klain Weaterill D 88,125 136,158 GJ 130,171 171 Krus S, see Kurkus J 109, Lazzari M, see Chierchia S Linden R J, Sreehararl N 171 64, 67 129,171 Kubo T, see Takeuehi J 99, Leach EH, see Burn JH Linden RJ, see Coleridge 178 5, 10, JCG 17,20,54,67 Kuhar M J, see Young WS Leavitt ML, Miller RE, Kotehen Linden R J, see Hainsworth 81,180 TA 140, 171 R 11,68 Kuhl U, see Kaczmarczyk G Ledsome JR, Linden RJ Linden R J, see Kappagoda CT 103,168 126, 171 126,128,129,169 Kullmann R, see Wasserman K Ledsome JR, see Mason JM Linden RJ, see Knapp MF 133,179 100, 1 72 127, 170 Kumada N, Nogami K, Sagawa Lee JB, see McGriffJC 106, Linden RJ, see Ledsome JR K 58,69 172 126,171 Kuntz A 46, 69 Lee MR, see Oates NS 84, Linden R J, see Sivananthan Kunze DL, see Beacham WS 173 N 125,176 46, 66 LeekBF 33,69 Lindgren I, Olivercrona H Kunze DL, see Beacham WS LeesP 109,171 34, 70 96,149,159 Lefkowitz R J, see Hoffman Linigro AJ, see McGriff JC Kurkus J, Sadowski J, Gellert BB 82,167 106,172 R, Krus S 109,171 Lehoczky E, see Szenasi G Ling HW 4 Kurkus J, see Sadowski J 114,178 Lioy F, Malliani A, Pagani 103,110, 114, 176 Lemarehands H, see Benchetrit M, Recordati G, Schwartz Kurosaki M, see Nomura G G 110,159 PJ 50, 51, 70 108,173 Leriehe R, Fontaine R 34, L~oy F, Szeto PM 60, 70 69 Lis Y, see Bennett ED 131, Ladinsky H, see Consolo S Leroy J, see Hillemand B 160 6 76,167 Littler WA, Honour J, Sleight Lahar M, see Altlas D 81, Levinsky NG 147, 171 P. Stott FD 64, 70 158 Levinsky NG, see Blendis Livnat A, Zehr JE 137, Laks M, see Klein LA 109, LM 120,160 171 170 Lewis BA, see Johns EJ 102, Ljungqvist A 85, 171 Landsberg L, see Besarab A 116,168 Lloyd TC, Friedman JJ 131,160 Lewis E J, see Blaufox MD 100,171 Lang E, Szalay L 114, 111,112,160 Lofving B, see Folkow B 177 Lewis T 64, 69 104,164 Lang M, see Zucker IH 90, Lewis T, Kellgren JH 12, Lohmeier TE, see Hall JE 167 181 69 Lombardi F, Della Bella P, Lang WJ, see Bell C 102, Liang CC 131,171 Casati R, Malliani A 16, 103,159 Liard JF 152,1 71 25, 31, 32, 33, 35, 56, 70 194 Author Index

Lombardi F, Della Bella P, Majewski H, see Rand MJ Malvin RL, see Bonjour Casalone C, Malfatto G, 105, 175 J-P 108,160 Malliani A 45, 70 Malfatto G, see Lombardi F Malvin RL, see Fisher SJ Lombardi F, MaUianiA, 45, 70 137,164 Pagani M 41,42, 70 Malik KU, see McGriff JC Malvin RL, see Johnson MD Lombardi F, Patton CP, 141,t72 121,168 Della BeUa P, Pagani M, Malliani A 12, 17, 18, 20, 21, Malvin RL, see Stitze~ SO MaUiani A 56, 70 62, 65, 70 129, 1 77 Lombardi F, see Bishop VS Malliani A, Brown AM 34, Mancia G 157 52, 53, 54, 66 47, 70 Mancia G, Donald DE, Lombardi F, see Casati R Malliani A, Lombardi F 32, Shepherd JT 89,104, 16, 18, 25,26, 27, 28, 29, 35,65, 70 105,172 31, 32, 34, 35,67 Malliani A, Lombardi F, Mancia G, Romero JC, Strong Lombardi F, see Malliani A Pagani M, Recordati G, CG 147,172 13, 17, 18, 20, 21, 22, Schwartz PJ 13, 17, 18, Manders WT, see Pagani M 23, 32, 35,42, 49, 52, 20, 21, 22, 23, 35, 42, 72 60, 65, 70, 71 49, 52, 60, 71 Mann FC, see Block MA Lombardi F, see Pagani M Malliani A, Pagani M 16, 18, 116,160 47,49, 50, 60, 72 20, 36, 37, 38, 39, 59, 70 Manning JW, see Ammons Lombardi F, see Recordati G Malliani A, Pagani M, WS 136,158 23,72 BergamaschiM 54,59, Marchand GR, see WiUiamson Lombardi F, see Schwartz PJ 60, 71 HE 180 49, 56, 73 Malliani A, Pagani M, Recordati Margaria R, see Bronk DW Longoni AM, see Bergamaschi G, Schwartz PJ 18, 19, 20, 43,66 M 58,66 21,46, 61, 70 Mark AL, see Fink GD 155, Lonigro AJ, see McGriff JC Malliani A, Parks M, Tuckett 164 141,172 RP, Brown AM 33,40, Mark AL, see Takeshita A Louis WJ, see Jarrott B 81,168 50, 71 155,178 Lovenberg W, see Alexander Malliani A, Peterson DF, Mark AL, see Thames MD RW 84,158 Bishop VS, Brown AM 100,178 Lowitz HD, see Rumpf KW 50, 64, 71 Mark AL, see Walker JL 100, 143,176 Malliani A, Recordati G, 179 LownB 65, 70 Schwartz PJ 13, 16, 17, Mary DASG, see Linden RJ Ludwig C, see Cyon E 63, 67 18, 19,20, 21, 22, 23, 88,125, 1 71 Lueth HC, see Sutton DC 34, 24, 29, 30, 31, 32, 33, Mary DASG, see Knapp MF 73 35,40, 61, 71 127,170 Lukoshkova EV, see Khayutin Malliani A, Schwartz PJ, Masaki Z, see Brosnihan KG VM 34, 62, 69 Zanchetti A 43, 44, 45, 93,161 Lundberg A, see Carpenter D 63, 65, 70, 71 Maseri A, Severi S, Nes M De 45,67 Malliani A, see Bishop VS 64, 71 Lundberg A, see Engberg I 52,53,54,66 Maseri A, see Chierchia S 45,68 Malliani A, see Brown AM 64, 67 16, 31, 33, 35, 36, 47, 66 Mason JM, Ledsome JR Mac Farlane MD 149,171 Malliani A, see Casati R 16, 100,172 Macklem LJ, see Weaver LC 18, 25, 26, 27, 28, 29, 31, Massry SG, see Better OS 90,180 32, 34, 35, 67 113,160 Mac Leod VH, see Coote JH Malliani A, see Lioy F 50, Mass~ SG, see Chaimovitz C 96,162 51, 70 113,161 Magnussen M, see Olson U Malliani A, see Lombardi F Matsuguchi H, see Takeshita 106, 174 16, 25, 31, 32, 33, 35, A 60, 73 Magrini F, see Guazzi M 41,42, 45,46, 56, 70 McCall RB, Gebber GL 172 64, 68 Malliani A, see Pagani M McCoord AB, see Wehlan TJ Mahoney EP, see Bricker NS 47, 49, 50, 54, 55, 56, 112,180 116,161 57, 59, 60, 72 McCubbin JW, see Ferrario Mahoney L, see Brody MJ Malliani A, see Recordati G CM 93, 96,164 148,161 23, 32, 57, 72 McCulloch MW, see Rand MJ Mahoney LT, Haywood JR, Malliani A, see Schwartz PJ 105,175 Packwood WJ, Johnson AK, 49, 56, 65, 73 McDonald KM, see Boykin J BrodyMJ 148,171 Malpus CM, see Karim F 129,160 Maines JE, see Williams RL 88, 100, 103,124, McDonald KM, see Hertrich 109,180 169 WL 143,167 Author Index 195

McDonald KM, see Taher MS Mitchell SW, see Grange RG Murao S, see Uchida Y 18, 118, 135,138,178 La 129,171 20, 21, 22, 23, 24, 25, 32 McDonald KM, see Torrente A Mitsanyi A, see Fedina L 94, 33, 34, 35, 56, 73, 74 De 125,126,162 164 Muratori G 36, 71 McGriff JC, Crowshaw K, Mittman U, see Chapman LW Murdock R, see Johns EJ Terragno NA, Linigro A J, 128,162 118,147,168 Strand JC, Williamson MA, Mizeres NJ 17, 71 Murkherjee SR 46, 71 Lee JB, Ng KKF 106, Mizumura Y, see Takeuehi J Murphy T, see Graham RM 172 99,178 81,166 Me Griff JC, Growshaw K, Mohai L, see Szalay L 114, Murphy~WR, see Judy WV Terragno NA, Malik KU, 177 87,168 Lonigro AJ 141,172 Mohnhaupt R, see Mursch DA, Bishop VS McKendrick CS, see Effendigil Kaczmarezyk G 84, 129, 168 136,172 MC 131,163 Mohnhaupt R, see Reinhardt Muylder GG De 77,162 McLachlan EM, see Oldefield H-W 129,130,175 Myers BD, Deen WD, Brenner BJ 14, 71 Mohnhaupt R, see Simgen B BM 101,102,172 McLain LG, see Taher MS 129,1 76 118, 135,138,178 Mohrland JS, see Knuepfer Naftilan AJ, see Katholi RE McLane-Vega L, see Schneider MM 98,170 152,153,169 E 110,176 Molinoff PB, see Minneman Nagatsu T, Rurt LA, Dequattro McNaUy H, see Randall WC KP 82, 172 V 84, 172 43, 72 Montgomery S, Jose P, Spiro Nakamura H, see Calaresu FR McNeil JS, see Nies AS 109, P, Slotkoff L, Eisner G 96,148,161 173 172 Nakamura H, see Takeuehi J McRitehie R J, see Vatner SF Moore-Ede MC, see Kass DA 95, 124, 178 58, 74 125,169 Nakamura M, see Takeshita A McSwiney BA, see Dowman Mootry PJ, see Stinson JM 60,73 CBB 46, 67 100,177 Nakayama s, see Takeuehi J Meekler RL, see Weaver LC Morel F 131,172 99,178 45, 74, 92,180 Morel F, Imbert-Teboul M, Nasjletti A, see Blasingham MC Medgett IC, see Rand MJ Chabardes D 131,172 106,160 105,1 75 MorgunovN 83,157,172 Nasjletti A, see Diz DI Meehan JP, see Chapman LW Morgunov N, Baines AD 152,163 128,162 84, 85,172 Neil E, see Heymans C 13, Melamed E, see Atlas D 81, Morgunov N, see Baines AD 69 158 83,158 Nerdmm T, see Baker DG Mercer PF, see Kline RL Morgunov N, see Baines A 29, 32, 34, 35, 56, 66 115,152,153, 1 70 83, 84,131,158 Nes M De, see Maseri A 64, Merrill JP, see Blanfox MD Morris BJ, Reid IA 135, 71 111,112,160 175 Nero FR, Brasil JCF, Antonio Merrill JP, see Bricker NS Moruzzi G 58, 71 A 56, 71 116,161 Moss NG, Harrington WW Nettleship WA 15, 71 Merrill JP, see Hollenberg NK 115,151,172 Ng KKF, see Burn JH 10 103,155,167 Moss NG, see Colindres RE Ng KKF, see McGriff JC Meyling HA 15, 71 150,162 106,172 Miekler RL, Weaver LC 90, Moss NG, see Recordati GM Nies AS, NeNeil JS, Sehrier 180 96, 97, 1 75 RW 109, 173 Migone L, see Andreucci VE Mow M, see Brody MJ 148, Nies AS, see Data JL 143, 101,158 161 162 Miller MR, Kasahara M 15, Mroczek WJ, Davidov M, Nies AS, see Gerber JG 71 Gabrilovich L, Finnerty 142,144,165 Miller RE, see Leavitt ML FA 109,172 Nies AS, see Olson RD 140, 140, 171 Mueller RA, see Bello-Reuss 141,143,173 Mills IH, Osbaldiston GW E 108,159 Niijima A 80, 95, 97,100, 129, 172 Muldowney FP, see Barger 131,173 Minneman KP, Pittman RN, AC 109, 112, 117,119, Nilsson IM, see Kopp U Molinoff PB 82, 1 72 122,159 116,138,144,170 Mirsky I, see Pagani M 72 Muller J, see Barajas L 78, Ninomiya I, Fujita S 94,1 73 Mitchell GAG 15, 71, 77, 99, 159 172 Ninomiya I, Irisawa H, WooUey Mulhns MM,Banks RO 154,172 G 94,173 196 Author Index

Nishi K, Sakanashi M, Olivari MT, see Guazzi M Pagani M, Pizzinelli P, Furlan TakenakaF 18,22,24, 64, 68 R, Guzzetti S, Malliani A 29, 32, 33, 35, 40, 56, 71 Oliver JA, Pinto J, Sciacca 54, 59, 72 Nogami K, see Kumada N RR, Cannon PJ 86, Pagani M, PizzineUiP, Furlan 58,69 106,143,173 R, Guzzetti S, Rimoldi O, Nohara H, see Takeuchi J Olivercrona H, see Lindgren Malliani A 56, 57, 72 95,124,178 I 34, 70 Pagani M, Schwartz PJ, Banks Noland PL, Reid IA 140, Oliw E, see Davila D 106, R, Lombardi F, Malliani A 173 143,162 47,49, 50, 60, 71 Nomura G, Arai S, Uno D, Olson PS, see Beierwaltes WH Pagani M, Schwartz PJ, Shimao M, Takata M, 144,159 Bishop VS, Malliani A 72 Takabatake T, Hattori N Olson RD, Nies AS, Gerber Pagani M, Vatner SF, Baig H, 109,173 JG 140, 141,173 Braunwald E 57, 72 Nomura G, Kibe Y, Arai S, Olson RD, Skoglnnd ML, Pagani M, see Bishop VS Uno D, Takeuchi J 108, Nies AS, Gerber JG 52,53,54,66 173 143,173 Pagani M, see Lioy F 50, 51, Nomura G, Kurosaki M, Olson RD, Gerber JG 144, 70 Takabatake T, Kibe Y, 165 Pagani M, see Lombardi F Takeuchi J 108,173 Olson U, Magnussen M, Eilersten 41, 42, 46, 56, 70 Nomura G, Takabatake T, E 106, 174 Pagani M, see MaIliani A Arai S, Uno D, Shimao M, Oparil S, see Katholi RE 13, 16, 17, 18, 19, 20, 21, Hattori N 108,173 152,153,169 22, 23, 35,36, 37, 38, 39, Nomura G, see Takeuchi J Oparil S, see Wallach R 42, 46, 49, 52, 54, 59, 60, 99,178 65, 74 61, 70, 71 Nonidez JF 15, 16,41, 71 Oparil S, see Winternitz SR Pagani M, see Recordati G Noresson E, Ricksten S-E, 152,180 32, 57, 72 Thoren P 155,173 Opgertroth T J, Wappel M, Pagani M, see Schwartz PJ Noresson E, see Rieksten S-E Zehr JE 143,174 49, 56, 73 87,90,155,175 Orden DE Van, see Williamson Pagani M, see Vatner SF Noresson E, see Thoren P HE 180 58,74 155,179 Osbaldiston GW, see Mills IH PangPKT 157 Norxis B, see Concha J 99, 129, 172 Pang PKT, Uchiyama M, 162 Osborn JR 157 SawyerWH 78,110, NorveilJE 77,112,157, Osborn JL, Di Bona GF 157, 174 173 174 Pang PKT, see Gallardo R Norvelt JE, Weitsen HA, Osborn JL, Di Bona GF, 109,165 Sheppek GG 79,173 Thames MD 135,138, Pannier R 43, 72 NorveU JE, see Weitsen HA 139, 141,142,147,174 Pantridge JF 64, 72 79,180 Osborn JL, see Di Bona GF Pantridge JF, see Webb SW 123, 133,136, 162,163 64, 74 Oates JA, see Frolich JC Osborn JL, see Francisco LL Pappenheim S 76,1 74 143,164 143,149,164 Parker RHO, see Burn JH 9 Oates NS, Ball SG, Perkins Osborn JL, see Thames MD Parks M, see MaUianiA CM, Lee MR 84,173 145, 178 33, 40, 50, 71 Oberg B, White S 104,173 Osgood RW, see Stein JH Pasquale NP' De, see Burch GE Oberg B, see Kendrick E 120,177 35,67 105,169 Oya N, see Takeuehi J 77, Pastoriza E 132,174 Oberg B, see Wennergren G 87,99,178 Pastoriza-Munoz E, see Bello- 130,180 ReussE 108,159 Obrist PA, see Grignolo A Pablo NC, see Cacciaguida Patton CP, see Lombardi F 131,166 RJ 109,161 46, 56, 70 Obrist PA, see Koepke JP Packwood WJ, see Mahoney Paulsen PJ, see Hertrich WL 131,170 LT 148,171 143,167 Oehl RS, see Weaver LC Pagani M 36, 71 Pearson JE, Williams RL 45, 74,90,92,180 Pagani M, Mirsky I, Baig H, 119,174 Ohata CA, see Foreman RD Manders WT, Kerkhof P, Pearson JE, see Williams RL 65, 68 Vatner SF 72 109,180 Ohya N, see Takeuchi J Pagani M, Pizzinelli P, Pearson MJ, see Kappagoda 95,124, 178 Bergamaschi M, Malliani A CT 126,169 Oldefield BJ, McLachlan 54, 55, 56, 59, 60, Pearson MJ, see Knapp MF EM 14, 71 72 127,170 Author Index 197

Peart WS, see Gordon D Pogghtsch H 76, 174 Recordati G, see Malliani A 110,166 Polese A, see Guazzi M 64, 13, 16, 17, 18, 19, 20, 21, Pederson HJ, see Seagard JL 68 22, 23, 24, 29, 30, 31, 32, 14, 73 Polhemus RE, Hall DA 132, 33, 35, 40, 42, 46, 49, Pelazo J, see Felder R 174 52, 60, 61, 70, 71 82,164 Pomeranz BH, Birtch AG, Reeordati GM 157 PeUetier CL, Shepherd JT, Barger AC 103,174 Recordati GM, Moss NG, 94,104, 105,174 Porush JG, see Cacciaguida Genovesi S, Rogenes PR PeUetier CL, see Clement DL RJ 109,161 97,175 85, 89, 90, 93,162 Powis DA, Donald DE 136, Recordati GM, Moss NG, Pelyao J, see Felder R 82, 140,174 Waselkov L 96, 97, 1 75 164 Prosnitz EH 157,174 Reeordati GM, Spielman WS Pines YL 96, 97,174 Prosnitz EH, Di Bona GF 93,175 Penna PE, see Karim F 88, 88, 95,100, 103,109,124, Reid IA, Morris BJ, Ganong WF 100, 103,124,169 127,128, 174 135,175 Perez-Gonzales JF, see Coote Prosnitz EH, Zambraski EJ, Reid IA, Schrier RW, Early JH 58, 67 Di Bona GF 122,174 LE 140, 175 Periti M, see Schwartz PJ Prosnitz EH, see Zambraski Reid IA, see Noland PL 65, 73 EJ 99,100,181 140,173 Perkins CM, Oates NS 84, Purkinje JE 8 Reimann KA, Weaver LC 173 Purtock RV, Colditz JH yon, 56,72,92,175 Perl ER 34, 65, 72 Seagard JL, Igler FO, Zuperku Reimann KA, see Waever LC Perl ER, see Beaeham WS EJ, Kampine JP 51, 92, 179, 180 46, 66 72, 90, 101, 174 Reinhardt HW 157 Perl ER, see Burgess PR 17, Purtock RV, see Kostreva DR Reinhardt H-W, Behrenbeck 22, 26, 33, 34, 43, 67 22, 69 DW 84,175 Perl ER, see Fernandez de Reinhardt H-W, Kaczmarczyk Molina A 46, 68 Quinby WC 116,175 G, Mohnhaupt R, Simgen Perl ER, see Franz DN 46, B 129,130,175 68 Rand MJ, see Burn JH 5, 6, Reinhardt H-W, Kaczmarczyk Peterson DF, Bishop VS 10, 79,161 G, Mohnhaupt R, Simgen 57, 72 Rand MJ, Majewski H, Medgett B, Wegener S 129,130, Peterson DF, Brown AM IC, McCulloeh MW, Story DF 175 50,63, 72 105,175 Reinhardt H-W, see Peterson DF, Kaspar RL, Randall DC, Hasson DM, Brady Kaezmarezyk G 84,103, Bishop VS 57, 72 JV 58,72 129,168 Peterson DF, see Bishop VS Randall WC, McNally H, Reinhardt H-W, see Simgen 58, 66 Cowan J, Caliguki L, Roshe B 129,176 Peterson DF, see Malliani A WG 43,72 Reves JG, see Wallach R 50, 64, 71 Ranges HA, see Smith HW 65, 74 Pettinger W, Sanchez A, 101,1 77 Reynolds GP, Ceasar PM, Gandler T, Sanehez J, Ranson SW, Billingsley PR Ruthven CRJ, Sandier M Saavedra J 82,174 13, 14, 16, 72 85,•75 Pettinger WA, see Berthelsen Rapaport S, see Kaplan SA Riehards AN, Plant OH S 105,160 108,169 101,175 Pettinger WA, see Graham RM Rashid A, see Hollenberg NK Riehins CA, Brizzee K 46 81,166 103,167 72 Phillips G, see Adrian ED Recordati G, Genovesi S, Cerati RiekstenS-E 155,157, ~7,158 D, Dicintio R 151,175 175 Pickering GW, see Smyth HS Recordati G, Lombardi F, Ricksten S-E, Thoren P 56, 73 Bishop VS, MaUianiA 155,175 Pinto J, see Oliver JA 86, 23,72 Ricksten S-E, Noresson E, 106, 143,173 Recordati G, Schwartz PJ, ThorenP 87,90. 155, Pittman RN, see Minneman KP Pagani M, Malliani A, Brown 175 82,172 AM 32, 57, 72 Ricksten S-E, Yao T, Di PizzineUiP, see Pagani M Reeordati G, see Bishop VS Bona GF, Thoren P 87, 54, 55, 56, 57, 59, 60, 72 52, 53, 54, 66 93,94, 153,154,175 Plant OH, see Riehards AN Recordati G, see Lioy F Ricksten S-E, Noresson E 101,175 50,51, 70 155, 173 198 Author Index

Ricksten S-E, see Thoren P Sabatini S, see Arruda JAL Schmid PG, see Thames MD 87,153,155, 179 134,158 126, 178 Rieben PA, see Salisbury PF Sadowski J 157 Schmidt CF, see Aviado DM 64, 73 Sadowski J, Kurkus J, 64, 66 Riedel W 157 Gellert R 103, 110, 114, Sehmidt M, see Honig A Rimoldi O, see Pagani M 176 123,167 56,57,72 Sadowski J, see Kurkus J Schneider E, McLane-Vega L, Rios LL, see Di Bona GF 109, 171 Hanson R, Childers J, 115,116,150,154,163 Sagalowsky AI, see Graham Gleason S 110, 176 Robertson GL, see Torrente RM 81,166 Schneider EG, see Standhoy ADe 125,126,162 Sagawa K, see Kumada N JW 109,177 Robie NW 105,175 58, 69 Schoelkopf L, see Felder R Robinson J, see Burn JH 9 Sakai S, see Takeuchi J 82,164 Roechini AP, Barger AC 77, 87, 95, 99,124, 178 Schramm LP, Carlson DE 136,175 Sakanashi M, see Nishi K 105, 176 Roechini AP, Cant JR, 18, 22, 24, 29, 32, 33, 35, Schramm LP, see Carlson DE Barger AC 85,175 40, 56, 71 105,161 Rogenes PR, Gottschalk WC Salisbury PF, Cross CE, Schtier R W 76, 116, 176 110,176 Rieben PA 64, 73 Schrier RW, Humphreys MH, Rogenes PR, see Recordati Salvo J Di, Fell C 99,163 Ufferman RC 112, 176 GM 97,175 Sanchez A, see Pettinger W Sehrier RW, see Bed T 144, Rogers SD, see Gilmore JP 82,174 160 101,165 Sandier M, see Reynolds GP Schrier RW, see Boykin J Romero JC, Dunlap CL, 85,175 129,160 Strong CG Sanford SE, see Graham RM Schrier RW, see Henrich WL 143,176 81,166 143,144, 167 Romero JC, see Beierwaltes Santiesteban HL, see Ammons Schrier RW, see Kim JK 76, 169 WH 144, 159 WS 136, 158 Schrier RW, see Nies AS 109, 1 73 Romero JC, see Blackshear JL Sassard J, see Grandjean B Schrier RW, see Reid IA 143,160 136, 166 140, 175 Romero JC, see Maneia G Sato A, see Calaresu FR Schrier RW, see Tatter MS 147, 172 96,148, 161 118, 135, 138,178 Roshe WG, see Randall WC Sato K, see Abe K 143, Schrier RW, see Torrente A 43, 72 158 De 125,126,162 Rosing DR, see Grossman Sato M, see Abe K 143, Schryver S, see Beierwaltes RA 129, 166 158 WH 144, 159 Roth LJ, see Dinerstein RJ Sawchenko PE, Friedman MI Schultz HD, Fater DC, Sundet 82,103,163 131,176 WD, Goetz KL 130, 176 Rouffignac C De, see Bencsath Sawin LL 157 Schultz HD, see Fater DC P 108,159 Sawin LL, see Di Bona GF 130, 163 Roughgarden JW 64, 72 111,112, 163 Schulze G, see Simgen B Rouot BR, Snyder SH 81, Sawin LL, see Francisco LL 129, 1 76 176 153,154, 164 Schwartz PJ, Brown AM, Row BP, see Forrest JM De Sawyer WH, see Gallardo R MaUiani A, Zanchetti A 143,162 109,165 65, 73 Ruffman K, see Gross R Sawyer WH, see Pang PKT Schwartz P J, Foreman RD, 103, 104, 122,136,166 78, 110, 174 Stone HL, Brown AM Rumpf KW, Frenzel S, Lowitz Schad H, Seller H 87, 93, 65, 73 HD, Scheler F 143,176 176 Schwartz PJ, Pagani M, Rurt LA, see Nogatsu T Scheler F, see Rumpf KW Lombardi F, Malliani A, 84, 172 143,176 Brown AM 49, 56, 73 Rushmer RF, Smith OA, Schiffrin EL, Garcia R, Schwartz PJ, Periti M, Lasher EP 58, 73 Gutkowska J, Boucher R, Malliani A 65, 73 Ruthven CRJ, see Reynolds Genest J 146, 176 Schwartz PJ, see Lioy F GP 85,175 Schilling JA, see Wehlan TJ 50, 51, 70 RyaU RW, see Engberg I 112, 180 Schwartz P J, see MaUiani A 45, 68 Schimmnck B, see 13, 16, 17, 18, 19, 20, 21, 22, Kaczmarzyk G 84, 168 23, 24, 29, 30, 31, 32, 33, 35, Saavedra J, see Pettinger W Schmid HE, see Grange RG 40, 42, 43, 44, 45, 46, 49, 52, 82, 174 La 117,135, 171 60, 61, 63, 65, 70, 71 Author Index 199

Schwartz PJ, see Pagarti M Sheppek GG, see No.ell JE Slick GL, Aguilera AJ, 47, 49, 50, 60, 72 79,173 Zambraski EJ, Di Bona GF, Schwartz PJ, see Reeordati G Sherrington CS 12, 13, 34, Kaloyanides GJ 117, 32, 57, 72 45, 60, 63, 73 118,176 Sciacca RR, see Oliver JA Sherrington CS, see Woodworth Slick GL, Di Bona GF, 86,106, 143,173 RS 60, 74 Kaloyanides GJ 113,176 Scidi AG, see Caretero OA Sherwin R, see Haven J De Sloop CH, see Grange RG La 147,161 85,111,162 117,135,171 Scott CK, Vanderwende C Shier DN, see Johnson MD Slotkoff L, see Montgomery S 82, 176 121,140, 168 172 Scott MT, see Stinson JM Shimao M, see Nomura G Smimov A 14, 73 100, 177 108, 109, 1 73 Smith H, see Yun J 143, Seagard JL, Pederson HJ, Shimizu H, see Takeuehi J 180 Kostreva DR, Horn DL 99,178 Smith HW 76, 101,110, van, Cusik JF, Kampine Shimizu H, see Ueda J 99, 177 JP 14, 73 179 Smith HW, Chasis H, Goldring Seagard JL, see Kampine JP Shinoda A, see Takeuchi J W, Ranges HA 101,177 91,169 95,124, 178 Smits JFM, see Stryuker- Seagard JL, see Kostreva DR Shropshire AT, see Baum T Boudier HAJ 154, 177 150, 170 95, 96, 159 Smith LR, see Waliach R 65, Seagard JL, see Purtock RV Shvalev VN 77, 176 74 51, 72, 90, 101,174 Silva P, see Besarab A 131, Smith OA 58, 73 Seller H 157, 176 160 Smith OA, see Rushmer RF Seller H, see Selmd H 87, Silverman AJ, see Barajas L 58,73 93,176 78, 99,159 Smyth HS, Sleight P, Serban I, see Eilahou HE Simgen B, Kaczmarczyk G, Picketing GW 56, 73 82,163 Mohnhaupt R, Schulze G, Snavely MD, see Insel PA Serban I, see Gavendo S Reinhardt H-W 129, 176 81, 82, 168 82, 165 Simgen B, see Reinhardt H-W Snow HM, see Kappagoda CT Severi S, see Maseri A 64, 129, 130, 175 126, 129, 169 71 Simonetti I, see Chierchia S Snyder SH, see Rouot BR Seyberth HW, see Frolich JC 64, 67 81,176 143,164 Singer B, see Johns EJ 102, Snyder SH, see U'Prichard Seymour AA, Zehr JE 176 116,118,147,168 DC 81, 179 Seymour AA, see Forrest Singer B, see Kaczmarezyk G Solandt DY, see Bronk DW 3M De 143,162 129,168 43, 66 Shade RE, see Blasingham MC Singh BN, see Figueras J 64, Sole M, see Wilson DR 108, 106,160 68 180 ShatTer RA, see Berecek KH Singh M, see Gupta PD 53, Sole MJ, see Stephenson RK 153,160 68 84, 177 Shaffer RA, see Knuepfer Sinits JFM, see Struyker- Solomon H, see Hollenberg MM 98,170 Boudier HAJ 154,177 NK 155, 167 Shaffer RA, see Touw KB Sivananthan N, Kappagoda Somers RJ, see Jarrott B 81, 153,179 CT, Linden RJ 125, 168 Share L, see Blasingham MC 176 Sonina RS, see Khayutin VM 106, 160 Sjolander M, see Kopp U 34, 62, 69 Shear L, see Katz MA 116, 145,146,170 Spencer HW, Yarger WE 169 Skoglund CR, see Biilbring E 115, 177 Shelley HJ, see Biilbring E 9 Spielman WS, see Blackshear 9 Skoglund ML, see Olson RD JL 143,160 Shemasky JH, see Vaughan 143,173 Spielman WS, see Colindres ED 149, 179 Slater JDH, see Wilcox CS RE 150, 162 Shepherd JT, see Clement DL 111,180 Spielman WS, see Knox FG 85, 89, 90, 93,162 Sleight P, Widdicombe JG 114, 170 Shepherd JT, see Donald DE 29, 73 Spielman WS, see Recordati 87, 99, 135,163 Sleight P, see Littler WA GM 93, 175 Shepherd JT, see Mancia G 64, 70 Spinelli FR, see Stinson JM 89,104, 105, 172 Sleight P, see Smyth, HS 56, 99, 177 Shepherd JT, see Pelletier CL 73 Spiro P, see Montgomery S 94, 104, 105,174 Shck GL 157 172 200 Author Index

Spyer KM 96, 157,177 Stott FD, see Littler WA 64, Taher MS, McLain LG, Spyer KM, see Hilton SM 96, 70 McDonald KM, Schrier RW 167 Strand JC, see Knox FG 114, 118, 135, 138, 178 Sreeharan N, see Kappagoda 170 Tainter ML, see Burn JH 9 CT 128, 169 Strand JC, see McGriff JC Takabatake T, see Nomura G Sreeharan N, see Linden RJ 106, 172 108, 109, 173 129, 1 71 Strong CG, see Mancia G 147, Takacs L, Bencsath P, Szalay Staffon RA, see Bricker NS 172 L 108, 109, 113,178 116,161 Strong CG, see Romero JC Takaes L, Bencsath P, Szenasi Standhoy JW, Schneider EG, 143, 176 G 113,178 Willis LR, Knox FG 109, Struyker-Boudier HAJ, Essen Takacs L, see Bencsath P 108, 177 H van, Sinits JFM, Evenwel 109,159 Stanton CJ, see Ayus JC 151, R 154,177 Takacs L, see Kottra G 93, 158 Stryuker-Boudier HAJ, Stairs 149, 170, 171 Stanton C_J, see Humphreys JFM, EvenwelR 154,177 Takacs L, see Szalay L 114, MH 151,168 Stuart PJ, see Kline RL 115, 177 Stanziate R, see Andreucci VE 153, 170 Takacs L, see Szenasi G 114, 101,158 Sulzman FM, see Kass DA 178 StarkeK 105,177 125,169 Takacs MD 157 Staszewska-Barzak J, Dusting Sundet WD, see Fater DC Takata M, see Nomura G 109, GJ 63, 73 130, 163 173 Staszewska-Barzak J, Ferreira Sunder WD, see Goetz KL Takeda T, see Takeuchi J 99, SH, Vane JR 50, 73 129,165 178 Stein JH, Osgood RW, Fen-is Sundet WD, see Schultz HD Takenaka F, see Nishi K 18, TF 120, 177 130, 176 22, 24, 29, 32, 33, 35, 40, Stein RM, see Kinney MJ Sutton DC, Lueth HC 34, 56,71 128,129,169 73 Takeshita AL 93, 1 78 Steiner RW, Blantz RC 102, Svensson L, see Kopp U 139, Takeshita A, Mark AL, Brody 177 170 MJ 155,178 Steiner RW, Tucker BJ, Blantz Swan HJC, see Figueras J Takeshita A, Matsuguchi H, RC 102,177 64, 68 Nakamura M 60, 73 Steiner RW, see Tucker BJ Sweetman BJ, see Frolich JC Takeshita A, see Fink GD 102, 179 143,164 155,164 Stella A 157 Szalay L, Bencsath P, Takacs Takeuchi J, Aoki S, Nomura G, Stella A, Dampney RAL, L 114, 177 Mizumura Y, Shimizu H, Golin R, Zanchetti A 136, Szalay L, Colindres RE, KuboT 99,178 177 Jackson R, Adkinson JT, Takeuchi J, Iino S, Hanada SteUa A, see Calaresu FR Lassiter WE, Gottschalk CW S, Sakai S, Oya N, Kitamura 148,161 114,178 K 77, 87, 99,178 Stella A, see Dampney RAL Szalay L, Lang E, Bencsath P, Takeuchi J, Ohya N, Sakai S, 136,162 Mohai L, Fischer A, Takacs Nakamura H, Nohara T, SteUa A, see Golin R 148, L 114,177 Hiasawa K, Shinoda A 95, 166 Szalay L, see Bencsath P 108, 124, 178 Stephenson RK, Sole MJ, 109, 159 Takeuchi J, Uchida E, Nakayama Baines AD 84, 177 Szalay L, see Takacs L 108, S, Takeda T, Yagi S, Inoue G, Stephenson WH, see Gaham 109,113,178 UedaH 99,178 RM 81,166 Szenasi G, Bencsath P, Takeuchi J, see Nomura G Stinson JM, Barrles AB, Lehoczky E, Takacs L 114, 108, 173 Zakheim RM, Chimoskey 178 Taquini AC, Aviado DM 44, JE, Spinelli FR, Barger AC Szenasi G, see Takacs L 113, 73 99, 177 178 Tarazi RC, Estafanous FG, Stinson JM, Mootry PJ, Szeto PM, see Lioy F 60, 70 Fouda FM 65, 73 Jackson CG, Gates HO, Szidon FP, see Kahl FR 100, Tarazi RC, see Estefanous FG Scott MT 100,177 169 65, 68 Stitzer SO, Malvin RL 129, Szidon JP, see Grossman RA Terragno NA, see McGriff JC 177 129,166 106,141, 1 72 Stone HL, see Schwartz PJ Szilagyi JE, see Brosnihan KG Terzian AR, see Willis LR 64, 73 93, 161 84, 180 Story DF, see Rand MJ Thames MD 92, 99, 135, 105, 1 75 157, 178 Author Index 201

Thames MD, Abbound FM 91, Troen BR, see Johnson MD Vatner SF 103, 179 100, 105,178 140, 144,168 Vatner SF, Boettcher DH, Thames MD, Di Bona GF Truelove LH, see Burn JH 9 Heindrickx GR, McRitchie 146, 147, 178 Tucker BJ, Blantz RC 102, RJ 58,74 Thames MD, Klopfenstein HS, 179 Vatner SF, Pagani M 58, 74 Abbound FM, Mark AL, Tucker BJ, Steiner RW, Vatner SF, see Pagani M 57, Wailer JL 100, 178 Gushwa L, Blantz RC 102, 72 Thames MD, Osborn JL, 179 Vaughan ED, Shemasky JH, DiBonaGF 145,178 Tucker BJ, see Blantz RC GiUenwater JY 149, 1 79 Thames MD, Sehmid PG 126, 102,160 Vaughan Williams EM, see 178 Tucker BJ, see Steiner RW Burn JH 10 Thames MD, Waickman LA, 102, 177 Velde J Van de, see Waele H De Abbound FM 89, 91, 145, Tuckett RP, see Malliani A 44, 67 178 33, 40, 50, 71 Vincent M, see Grandjean B Thames MD, see Felder RB 136,166 44, 63, 68, 82, 92, 164 Uchida E, see Takeuehi J Vogt Marthe 10 Thames MD, see Osbom JL 99,178 Volkman PH, see Goldberg LI 135,138, 139,141,142, Uchida Y 18, 20, 22, 23, 24, 102, 166 147,1 74 25, 36, 38, 39, 73, 91,179 Thames MD, see Wailer JL Uchida Y, Kamisaka K, Waele H De, Velde J Van de 100, 179 Murao S, Ueda H 18, 23, 44, 67 Thoenen H, see Consolo S 24, 25, 33, 34, 74 Waickman LA, Abboud FM 6 Uchida Y, Kamisaka K, Ueda 91,179 Thompson JR, see Judy WV H 97,179 Waickman LA, see Thames MD 87, 93,168 Uchida Y, Murao S 20, 21, 89, 91,145,178 Thompson JW, see Burn JH 22, 24, 32, 33, 34, 35, 56, Wakim KG, see Block MA 5,10 73,74 116, 160 Thoren P 57, 63, 73, 87, Uchida Y, see Ueda H 19, 20, Wailer JL, Thames MD, 91, 99, 104, 135, 157, 24, 33, 74, 96,148, 179 Abboud FM, Mark AL, 179 Uchiyama M, see Pang PKT Klopfenstein HS 100, Thoren P, Noresson E, 78, 110, 174 179 Ricksten S-E 155, 1 79 Ueda H, Uchida Y 96, 179 Walker JM 4 Thoren P, Ricksten S-E Ueda H, Uchida Y, Kaisaka Wailer JM, see Burn JH 10 87,153,155,179 K 96,148,179 Walker JL, see Thames MD Thoren PN, see Jarecki M Ueda H, Uchida Y, Kamisaka 100, 178 136,168 K 19, 20, 24, 33, 74, 96 Wall PD 57, 74 Thoren P, see Noesson E 179 WaUach R, Karp RB, Reves 155, 173 Ueda H, see Takeuchi J 99, JG, Oparil S, Smith LR, Thoren P, see Ricksten S-E 178 JamesTN 65, 74 87, 90, 93, 94, 153, 154, Ueda H, see Uchida Y 18, 23, Wang BC, see Goetz KL 155,175 24, 25, 33, 34, 74, 97,179 129, 165 Torrance RW, see Holmes R Ueda J, Kishimoto T, Shimizu Wang P, see Barajas L 77, 17, 19, 40, 69 H, Yamamoto K 99, 179 78, 79, 81, 99, 159 Torrente A De, Robertson Ufferman RC, see Schrier RW Wappel M, see Opgertroth TJ GL, McDonald KM, Schrier 112, 176 143, 174 RW 125,126,162 Uno D, see Nomura G 108, Wargo A, see Felder R 82, Torresani J, see Friggi A 109,173 164 95,164 U'Prichard DC, Snyder SH Waselkov L, see Recordati Touw KB, Haywood JR, 81, 179 GM 96, 97,175 Shaffer RA, Brody MJ Wassermann K, Huss R, 153,179 Vander AJ, see Cant JR Kullmann R 133, 179 Tranttm-Jensen J 14, 73 120, 161 Trendelenburg U, see Burn JH Vanderwende C, see Scott Watanabe AM, Judy WV, 10 CK 82, 176 Cardon PV 95, 179 Trevan JW, Book E, Burn JH, Vendewalle A, Farman N, Watanabe AM, see Judy WV Gaddum JH 8 Bonvalet J-P 154, 179 87,168 Trevino DL, see BelloReuss E Vane JR, see Staszewska- WoughWM 109, 179 118, 120,159 Barzak J 50, 73 Weatherill D, see Linden RJ Trippodo NC, see Hall JE Vannice J, see Dinerstein RJ 88, 125, 171 167 82,103,163 Weaver LC 50, 74, 90, 179 202 Author Index

Weaver LC, Danos LM, Oehl Williamson HE, Marchand GR, Zackheim RM, see Stinson JM RS, Meekler RL 45, 74. 92, Bourland WA, Farley DB, 99, 177 180 OrdenDE Van 180 Zambraski EJ 157 Weaver LC, Maeklem LJ, WiUiamsonMA, see MeGRfff Zambraski EJ, Di Bona GF Reimann KA, Miekler RL, JC 106,172 106, 118, 121, 135, 181 OehlRS 90,180 Willis LR, Lappe RW, Hendry Zambraski EJ, Di Bona GF, Weaver LC, Reimann KA DP, Evan AP, Temian AR KaloyanidesGJ 117, 119, 92,179 84, 180 121,122, 133,181 Weaver LC, see Reirnann KA Willis LR, see HoUingsead P Zambraski E J, Dunn MJ 56, 72,92,175 132, 167 107,181 Webb RL, Knuepfer MM, Willis LR, see Lappe RW 84, Zambraski EJ, Prosnitz EH, Brody MJ 149,180 86, 171 DiBonaGF 99,100, 181 Webb SW, Adgey AA, Pantridge Willis LR, see Standhoy JW Zambraski EJ, see Di Bona GF JF 64, 74 109, 177 118, 163 Weber P, see Larsson C 142, WillisWD, see CoggeshaU RE Zambraski EJ, see Prosnitz EH 171 17,67 122, 174 Weder AB, see Goldberg LI Wilson A, see Bennett ED Zambraski EJ, see Slick GL 133,134, 166 131,160 117, 118, 176 Wegener S, see Reinhardt H-W Wilson DR 113, 180 Zanchetti A, see Calaresu FR 129,130,175 Wilson DR, Hourath U 113, 148, 161 Weidinger H, Kirchner F 87, 180 Zanchetti A, see Dampney 180 Wilson DR, Honrath U, RAL 136,162 Weiss L-G, see Wennergren G Cusimano M 113,180 Zanchetti A, see Golin R 148, 130, 180 Wilson DR, Hortrath U, Sole M 166 Weitsen HA, NorveU JE 79, 108, 180 Zanchetti A, see Malliani A 180 Wilson JP, see Frolich JC 43,44,45, 63,65, 70, 71 Weitsen HA, see Novell JE 143, 164 Zanchetti A, see Schwartz PJ 79,173 Wilson MF, see Judy WV 65, 73 Wehland TJ, McCoord AB, 87, 93,168 Zanclietti A, see SteUa A Schilling JA 112, 180 Winaver J, Chaimovitz C, 136,177 Wennergren G, Hendriksson Better OS 113,180 Zehr JE, see Livnat A 137, 171 B-A, Weiss L-G, Oberg B Winternitz SR, Katholi RE, Zehr JE, see Opgenroth TJ 130,180 Oparil S 152, 180 143,174 Wennergren G, see Kendrick E Winternitz SR, see Katholi RE Zehr JE, see Seymour AA 176 105,169 152,169 Zimmer JA, see Cambell WB WestfaUTC 85,105,180 Wolgast M, see Hermansson K 144,161 Whitaker EM, see Kappagoda 119, 167 Zimmerman BG 85, 181 CT 126,169 Wollard HH 15, 36, 39, 74 Zimmerman BG, see Dunham White HL, see Heinbecker P Woodcock EA, Funder JW, EW 118, 147, 163 126,167 JohnstonCI 82, 180 Zimmerman BG, see Gomer White JC 34, 74 Woodworth RS, Sherrington SK 99,166 White S, see Oberg B 104, CS 60, 74 Zimmerman H, Ganong WF 173 Woolley G, see Ninomiya I 137,181 Whitteridge D, see Guttmann 94,173 Zimmerman H-D 78, 79,181 L 46, 68 Zucker IH, Gilmore JP 130, 181 Whitwam JG, Kidd C, Fussey Yagi S, see Takeuchi J 99, Zueker IH, Lang M, Hackley IV 94, 180 178 JF 90,181 Widdicombe JG, see Sleight P Yamabe H, see Alexander RW Zucker IH, see Echtenkamp 29, 73 84, 158 SF 89,163 Wilcox CS 157 Yamamoto K, see Ueda J 99, Zucker IH, see Gilmore JP Wilcox CS, Aminoff MJ, 1 79 124,130,165 SlaterJDH 111,180 Yao T 157 Zuperku EJ, see Bosnjak Wilcox CS, see Gordon D Yao T, see Rieksten S-E 87, ZK 32, 66 110,166 93, 94, 153, 154, 175 Zuperku EJ, see Hess GL Williams GM, see Forrest JM Yarger WE, see Spencer HW 23, 24, 69 De 143,162 115,177 Zuperku EJ, see Kampine JP Williams RL, Maines JE, YoungWS, Kuhar MJ 81,180 91,169 PearsonJE 109,180 Yun J, Kelly GM, Bartter FC, Zuperku EJ, see Kostreva DR Williams RL, see Pearson JE Smith H 143,180 22, 69 119, 174 Zuperku E J, see Purtock RV Williams TH 15, 74 51, 72,90, 101,174 Subject Index

acetylcholine 41,105 atrial receptors 20-23, 53, 61, 88, 89, 98, -, non-transmitter function 5 155

-, noradrenaline release by 6 - -, Paintal-type 125 -, ontogenetic development 6 ,reflex effects 100, 124ff -, release of, from CNS 4 - -, stimulation of, in monkey 130

acetylcholinesterase, renal 77-79, 99 - vagal receptors 23 acetylstrophanthidin 91, 92 atropine 52, 55, 99,105 adenylate cyclase receptors, renal 131 autonomic fibers, efferent 13

ADH 124-126,129 - nervous system 12

- bioassay technique 125,126 - reflexes 13 adrenal medulla, catecholamine secretion 4 autoregulation 104 adrenaline, actions of 4 autotransplanted kidney 116,154

- uptake 4 adrenergic innervation, tubular 108 baroreceptor input 98 - renal nerves 77ff -reflex 87,123,128 - terminals 99 , controlof 58 a-adrenergic receptor blockade 55, 56 , reduction in sensitivity 56 a-adrenoceptors, a-1 and ~-2 81, 82 baroreceptors, ionic sensitivity of 85 -, antagonists 95 -, reflex effects of 100 -, blockade of 109 bicucuUine and renorenal reflex 148 -, renal, presynaptic 105 bile duct, ligation of 113

- and renin release 140 biological assay, methods of 3

-, tubular 81, 82, 118, 124,131-133 - standardization 3 #-adrenoceptors, antagonists of 95 blood pressure regulation 59

-,/~-1 and ~-2 renal 81, 82 - volume changes 89, 90, 92, 93

-, blockade of 109,113,119 - - -, reflex effects 98

- and renin release 138-140, 144, 145,153 bradycardia 93 -, tubular 131-133 bradykinin 21, 24, 31, 33, 35, 43, 50, 56, 62, afferent terminals, sympathetic 14, 15 92, 127 9-amino-acridine-propranolol 81 -, algogenic action 57 anesthesia 114 Burn and Rand hypothesis 79 -, effect on reflex heart rate response 54 angiotensin II 85, 96, 118,121,127 capsaicin 94

- and renal circulation 101,102 carbohydrate intake 85 antinatriuresis 150,151 cardiac denervation and diuresis 129 antinatriuretic response 117,122, 123 - nociception 34, 35 aorta, inflation of 48, 50 -pain 19 -, local anesthesia of 50 - periodicity 21, 23 -, mechanoreceptors, sympathetic in 36-40 - receptors, reflex effects of 130 -, multiple terminals of receptors 40 , stimulation of 88, 89 -, occlusion of 26, 33, 47 - sensory fields, multiple 29 -, stretch of 50, 51,54, 59 - sympathetic nerve, recording from 16 arrhythmia 64 - vagal fibers 32 ascites 112, 113 cardiopulmonaryreceptors 89-91, 98, 105 asphyxia 39 cardiovascular reflexes 42ff atenolol 95,138,140 - - upon renal activity 87 atrial afferents, sensory field of 29 - reflexogenic areas 13

- filling 21 - regulation, stability of 60 - pressure 21, 22 carotid occlusion and renin release 136 204 Subjectlndex carotid sinus nerve, central projections 98 electron microscopy 14 emotion, hemodynamics in 58 - - perfusion 122 end-net formation 15 - - pressure 100 catecholamine excretion, renal 83-86 epinephrine and renal potassium 152

- and renin release 140,144 - metabolism, renal 83ff - receptors 81 - and sodium excretion 120,121 , renal, characterization of 131-134 ethacrynic acid 143 catecholamines, hypersensitivity to 5 exercise, hemodynamics in 58

- in renal nerve 78 catechol-O-methyl-transferase 83 fibrillation, ventricular 26, 27 cerebellum, inhibition of carotid sinus reflexes fluorescent histochemistry 77 58 furosemide 137 C fibers, afferent 94 chemical stimulation 43 ganglion, aorticorenal 77 chemoreceptor reflexes 123 generator potential, electrogenesis of 14 chemoreceptors, renal 97,151 glomerular filtration rate 102,106,108, chemosensitive endings, cardiac 22, 26 111,113,116 chemosensitivity of ventricular receptors glucose transport, renal 114 32,33 granular cells, juxtaglomerular 80 chemostimulation, cardiovascular 91 guanethidine 99, 109, 117,122, 148 chloride reabsorption 132 cholinerglc see also acetylcholine H + 32, 35 choimerglc fibers, sympathetic 6 haloperidol 103 - innervation, renal 78ff head-up tilt 136 circulation, neural regulation of 19 heart failure, congestive 117 clearance ratio for norepinephrine 86 -, innervation of 14, 15 clonidine 95 hemicholininm 6 hemodynamics and ventricular receptors - binding sites 81 conscious dogs, reflex effects in 122,123,129 24, 25 hepatorenalreflex 95,131 - -, renal denervation in 110 hexamethonium 112 - -, renin release in 136 140 histamine 105 -rats 153,154 coronary artery occlusion 26, 32, 33, 35, 57, homeostasis, circulatory 58-60 63, 91,137 5-HT 96, 137 , reflex effects of 43 5-HTP 95 , selective 92 6-hydxoxydopamine 81 - and acetylcholinesterase 79, 81 - flow and cardiac receptors 31ff hypercapnie acidosis 123 - receptors, sympathetic 35, 36 hypertension, arterial 60 -, role of renal nerves in 152-155 deccrebrate preparations 43, 60 hypertensive rats 82, 152-154 degeneration studies, selective 14 hypophysectomy 125,126 denervation, chronic, sino-aortic 45 hypotension hemorrhagic 144 dense-core vesicles 78 hypothalamus, anterior 148,153,154 depressor reflexes 57, 58 -, lateral 98 - -, vagal 63, 64 -, stimulation of 102 diabetes insipidus and extent of hypoxia 94 pituitary ablation 126 -, hypoxic 123 dibenamine 112 diuresis 93,150,152 idiopathic autonomic insufficiency 111 indomethacin 102, 106,107,140, 142 - upon renal denervation 107if, 117ff diuretic response, humoral mediators of 127 infarction, myocardial, and sympathetic DOCA-salt hypertensive rats 152,153 activity 64 L-Dopa 95, 96 ischemia, myocardial 19, 36, 45, 57, 63 - decarboxylase 84 isoprenaline 25 dopamine 96,133,134 isoproterenol 82, 119,120,132,133,140 - and tubular potential 132 - excretion 84, 85 -,renal 102,103 dopaminergic receptors 82 juxtaglomerular apparatus, innervation of 80 Doppler flow probe 56 - granular cells 78,139, 141 Subject Index 205 kaliuresis 108 phentolamine 55, 56, 132,133,141,148 kallikrein, renal 147 phosphate transport, renal 114 kidney see also renal plasma volume, regulation of 124 kidney, catecholamine receptors in 81,82 polymodalreceptors 33,43 -, innervation of 77 - -, atrial 22 -, regional distribution of blood flow 101 portal vein occlusion 100,131 -, sensory fibers of 79 positive feedback hypothesis, cardiovascular -, transplanted, sodium balance of 111, 112 58ff -, tubular irmervation 78ff potassium 21, 32, 92 -, vascular innervation 80, 81 - excretion 151

- homeostasis 151 liver cirrhosis 95 prazosine 133 -, sensory functions of 131 preoptic nucleus, lateral 97 lung inflation 42, 91 pressorreflexes 55,57 preterminals, excitation of 62 mechanical probing 19, 20, 30 probing, mechanical 61 mechanoreceptors, cardiac 20 propranolol 50, 55, 95,102, 113,131-133, -, renal 97 136,137 meclofenamate 106 prostaglandin 62, 105,106 mesenteric reflexes 95 - release 141,143, 147 methoxytyramine 83 - synthesis, inhibition of 118 metoprolol 139 prostaglandins and control of renin release microspheres 101 142-145 myelinated vagal fibers 130 pulmonary artery, occlusion of 44 myocardial contractility 50 - -,receptors in 40

- infarction, natriuresis in 131 - congestion 42

- ischemia 19, 36, 45, 57, 63, 92 - edema 131

, pathophysiology of 63 - vein, receptors in 41

natriuresis 85, 93,130,150,151 ramus communicans, recording from 16 -, exaggerated 154 receptor sensitization 33

- upon atrial receptor stimulation 127 reflex regulation of renin 135ff - upon renal denervation 107ff, 117ff, 121ff reflexes, cardiopulmonary 91, 93 nephrectomy, unilateral 151 -,hepatorenal 95,131 neuroanatomy, renal 75ff -, positive feedback component 60 neuroeffector junction 78 -, renal 148 nictitating membrane 4 renal see also kidney nociception, peripheral mechanisms for 34 renal afferents, central projections of 97, 98 noradrenaline see norepinephrine - -, reflex effects of 148,149 norepinephrine 82, 90,96,132 - artery occlusion 97

- and antinatriuresis 119 - blood flow 116 -, hypothalamic 152 - circulation, control of 99-107 -, release of 4, 6 - denervation 85,136, 152 -,renal 78, 103,115 , pharmacological 109, 116

- and renal circulation 101 - - technique 115 -, supersensitivity to 5 - - and tubular transport 107-116 normetanephrine 83 - hemodynamics 116 nucleus paraventricularis 98 - - in conscious dogs 103, 104

- traetus sotitarii 149 - - and prostaglandins 143 - hormonal systems, control of 135-147

orthostatic hypotension 111 - mechanoreceptors 150

- nerve recording 88

papaverine 143 - - stimulation 86

para-aminohippurate, renal transport of 114 - - - and kallikrein excretion 147

paraplegia 46, 61 - - - and prostaglandin release 147

parathyroid hormone 114 - - -, effects on renal function 116-121 paraventricular nucleus 98 - - - andrenin 135

pentolinium 112 - nerves, afferent 96-98

pericoronary nerves 32 - -, composition of 77 phenoxybenzamine 50, 86, 95,109, 110, 112, - -, electrical characteristics of 87ff 113,117,119,122,129,132,133,136,140,141 - -, physiological functions of 99ff 206 Subject Index renal plexus 77 sympathetic afferents, conduction velocity of - receptors 96, 97, 99 17

- reflexes, supraspinal control 149 - -,history of term 13 - sympathetic activitiy 45 - -, reflexes mediated by 42ff

- - - efferent 87ff, 114,117,131,154 - - in ventral roots 17 .... , alteration in 98 - baseline activity, importance of 44 .... , in hypertension 153 - centers, spinal 46

.... , inhibition of 94 - control ofrenin release 145ff .... , pulse-synchronous 103 - discharges, central regulation 96 .... , reflex changes in 121,148 - excitatoa2¢ reflex 63, 64

- tubules, adrenergic innervation 108 - fibers, cardiopulmonary 50

- vasodilatation, dopamine-induced 102,103 - innervation, cardiovascular 62 renin activity in plasma 136,137,142, 143, - nerve activity, cardiac 88 146 - - -, renal 84 - -angiotensin system, activity of 153 ,splenie 88 - release 104,106 - nonmyelinated fibers 14, 18, 20, 32, 38 - -, interaction of control mechanisms 145ff - outflow, differentiated control of 104 - -, regulation of 135ff - receptors, location of 19

- secretion 80 - reflexes 94, 95 renoadrenal reflex 151 - -, cardiocardiac 45, 48, 50 renocardiac reflexes 150 - -, mixed feedback 60 renorenalreflexes 147-152 - - and normal hemodynamics 45, 48 reserpine 5, 80,110 - -, spinal 93 reticular nucleus, paramedian 97 - -, supraspinal control of 45, 57, 60, 62

- tone, peripheral 152, 153 saralasin 102 sympathosympathetic loop 59, 60, 64 sensory endings in the heart 14 - reflexes 13, 19 serotonin 138 sympathovagal reflex 49 shock avoidance 131 single nephron glomerular filtration rate tachyarrhythmia, atrial 128 108,118 tachycardia 58 sino-aortic denervatio n 44,45,50 tegmental field, lateral 97 sodium absorption, reflex regulation 124,125 temperature, hypothalamic 94 - deprivation 93,102,106,143 thiocholine histoehemieal method 77

- excretion 141,151,152 thoracic inferior vena cava constriction

- intake and catecholamines 84, 85 112, 117 -reabsorption 133,154 transplantation and innervation, renal 79 - -, tubular 104,108ff, 116ff, 121ff L-tryptophan 137 - -sensitive rats 82 tubular transport processes, neural control of - and water balance regulation 98 107ff spinal cord, preganglionic renal level 77 tubuloglomerular feedback system 102

- - section 63,148,149 ---,chronic 52 unmyelinated fibers 118,148 stellate ganglion stimulation 124 ureteral obstruction 113 stress 58,110,131,154 uric acid transport, renal 114 supersensitivity 4,5 sympathetic see also cardiac, cardiovascular, vagal afferent fibers 15, 18, 23, 29, 32, 87-89, heart 91,93,98 sym ~athetic afferents 13, 98 ---,cardiac 58 - - cardiopulmonary 90, 91 vagotomy 57 - - cardiovascular 12, 92 varicosities, axonal 78

- - -, discharges of 18, 21, 22 vasoconstrictor responses 148, 153 - - -, excitatory reflexes 44ff, 58ff - -,renal 99,105,116

- - -, functional characteristics of 18ff vasodilator fibers, sympathetic eholinergic - - -, methodologY of investigation 15-17 99,109

- - -, morphologY of 14, 15 -response 148,153 - - -, with multiple endings 40 vena tara, occlusion of 26, 28, 47 - - -, myelinated 14, 18, 20, 32, 38 venous return, reflex actions of 44 - - -, noeiceptive function 12, 19, 34, 35, ventrieular afferents, nonmyelinated 62 45, 62 - -, sensory field of 29 , , pathophysiological significance 19 - fibrillation 62 Subject Index 207 ventriculaI myelinated afferents 23, 24 volume expansion, intravascular 137

- nociceptors 34-36 - receptors, intrathoraeic 125

- nonmyelinated afferents 25ff -, reflex regulation of 124,125

- pressure 24 - receptors, excitation of 23ff - stimuli for receptors 25 water absorption, reflex regulation of veratridine 24, 32, 35, 43, 50, 56, 90 124,125 visceral pain 12 - reabsorption 118 volume expansion 114,154 - transport, renal, control of 107ff