4. Electrical Stimulation of the Nerve of Pterygoid Canal Decreased Vascular Airway Resistance to Low-Voltage Stimulation

Home , Nerve of pterygoid canal, Pterygoid canal

Journal of Physiology (1989), 419, pp. 121-139 121 With 8 text-figures Printed in Great Britain

AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE AND AIRFLOW RESISTANCE IN THE ANAESTHETIZED DOG BY M. A. LUNG AND J. C. C. WANG From the Department of Physiology, University of Hong Kong, Sassoon Road, Hong Kong

(Received 31 March 1989)

SUMMARY 1. In pentobarbitone-anaesthetized dogs with constant-flow vascular perfusion of nasal mucosa on both sides, nasal airway resistance, vascular resistance, vascular capacitance (via changes in total venous outflow) and blood flow in the anterior and posterior venous systems were measured. 2. Electrical stimulation of the cut peripheral ends of the cervical sympathetic trunk, caudal nasal nerve, or major palatine nerve increased vascular resistance and decreased vascular capacitance and airway resistance. Propranolol and atropine had no effect on the responses while bretylium completely abolished them; phentolamine greatly lessened the vascular resistance response and partially decreased the vascular capacitance and airway responses. Hence, sympathetic stimulation causes constriction of the resistance vessels via a-adrenergic mechanism and constriction of capacitance vessels via a-adrenergic as well as some non-adrenergic and non- cholinergic mechanisms. 3. Denervation of the cervical sympathetic trunk, caudal nasal nerve and major palatine nerve decreased nasal vascular resistance and increased vascular capacitance and airway resistance, suggesting tonic sympathetic discharge to nasal mucosa via caudal nasal and major palatine nerves. 4. Electrical stimulation of the nerve of pterygoid canal decreased vascular resistance but increased vascular capacitance (in the posterior venous system) and airway resistance to low-voltage stimulation (below 10 V), and decreased vascular capacitance (in the anterior venous system) and airway resistance to high-voltage stimulation (above 10 V). Hexamethonium reversed the vascular resistance response as well as vascular capacitance and airway responses to high-voltage stimulation. Bretylium and phentolamine enhanced the vascular resistance response and reversed vascular capacitance and airway resistance responses to high-voltage stimulation. Hence, low-voltage stimulation results in parasympathetic dilatation of resistance and capacitance vessels whereas high-voltage stimulation results in parasympathetic dilatation of resistance vessels and sympathetic constriction of capacitance vessels. The parasympathetic vasodilatation was atropine resistant and the sympathetic vasoconstriction was partially via az-adrenergic mechanisms. 5. Denervation of the nerve of pterygoid canal did not affect vascular resistance, vascular capacitance or airway resistance suggesting negligible tonic parasympathetic and sympathetic discharges to nasal blood vessels via the nerve.

MS 7611 122 M. A. LUNG AND J. C. C. WANG 6. Simultaneous optimal stimulation of sympathetic and parasympathetic nerves resulted in vasoconstriction, especially in capacitance vessels, suggesting sympathetic predominance over parasympathetic control.

INTRODUCTION Many studies have already been carried out to investigate the influence of the autonomic nervous system on the vasomotor activity of the nasal mucosa (Tschalussow, 1913; Slome, 1955; Malcolmson, 1959; Jackson & Rooker, 1971; Malm, 1973; Anggard, 1974; Anggard & Edwall, 1974; Eccles & Wilson, 1974). The parasympathetic response is believed to be vasodilatation as electrical stimulation of the nerve of the pterygoid canal or the vidian nerve (which carries predominantly parasympathetic fibres to the nasal mucosa) causes an increase in nasal airway resistance (or a decrease in nasal patency) as well as an increase in venous outflow from the sphenopalatine vein. The sympathetic response is thought to be vasoconstriction as stimulation of the cervical sympathetic trunk causes a reduction in nasal airway resistance (or an increase in nasal patency) as well as a reduction in venous outflow from the sphenopalatine vein. Blood from the nasal mucosa drains via several pathways: normally about two-thirds via the dorsal nasal vein, one-third via the sphenopalatine vein and negligible quantities via veins of the underlying bony cavity and the palatine plexus (Lung & Wang, 1987 a). It is not known whether or not autonomic nervous stimulation exerts different or equal influence on all vascular channels. Therefore, venous drainage via a single pathway cannot be used as an index for total blood flow or vascular conductance of the nasal mucosa. In all previous studies on the autonomic nervous control of the nasal mucosa, nasal airway resistance or patency was measured under conditions of spontaneous blood flow and hence changes in this variable reflect not only the primary effect on the nasal capacitance vessels but also the passive effect due to concomitant changes in nasal blood flow. We have shown that nasal blood flow gives a linear correlation with nasal airway resistance (Lung & Wang, 1987 b). We have established the method of direct and simultaneous measurement of not only nasal vascular and airway resistances but also outflows from the sphenopalatine and dorsal nasal veins (Lung, Phipps, Wang & Widdicombe, 1984; Lung & Wang, 1987a). We have adopted this method to investigate the primary response of the resistance and capacitance vessels of the nasal mucosa to autonomic nervous stimulation. Some of the results have been presented in an abstract (Lung & Wang, 1987 c).

METHODS Mongrel dogs (body weight 20+ 1-8 kg; n = 45) of either sex were anaesthetized with sodium pentobarbitone (25 mg kg-') intravenously and supplementary doses were given if necessary. Body temperature (rectal) was maintained at 37 °C by means of an electric heating pad placed underneath the animal. Tracheotomy was performed and the tracheal cannula was connected to a Fleisch pneumotachograph to give airflow and tidal volume by electric integration. A femoral artery was cannulated for measurement of systemic arterial pressure. Heparin (1000 units h-') was given via a cannulated femoral vein. AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 123

Measurement of nasal vascular resistance In the dog, almost all nasal mucosal blood enters via the terminal internal maxillary artery and drains ultimately into the facial veins (Lung & Wang, 1987a). In preparation with constant-flow vascular perfusion of the nasal mucosa, vascular resistance can be calculated as the ratio of the pressure difference across the nasal vascular bed (perfusion pressure minus the facial venous pressure, mmHg) to its related perfusion flow rate (ml min-'). Vascular perfusion of the nasal mucosa was carried out as described previously (Lung et al. 1984). In brief, an infraorbital dissection was made along the zygomatic region to expose the internal maxillary artery and its infraorbital and terminal branches. The internal maxillary artery just proximal to the terminal branch was closed with a snare. The terminal branch was perfused, via the infraorbital catheter, with blood from a reservoir filled from a femoral artery; perfusion was carried out at a constant rate by means of a peristaltic pump. The perfusion pressure was measured from a point between the pump and the infraorbital catheter. The perfusion rate was adjusted to give a perfusion pressure close to systemic arterial pressure. Perfusion was performed on both sides with separate pumps. Measurement of nasal vascular capacitance In constant-flow perfusion experiments, the same total flow would be distributed through the vascular channels per unit time. Hence, a temporary decrease in total venous outflow through all vascular channels indicates an increase in total vascular capacitance whereas a temporary increase in total venous outflow through all vascular channels indicates a decrease in total vascular capacitance. Dorsal nasal and sphenopalatine venous outflows and pressures were measured as described previously (Lung & Wang, 1987a). In brief, blood from the dorsal nasal vein on both sides was bypassed into the left facial vein and measured with a cannulating-type electromagnetic flow sensor. In the same way, blood from the sphenopalatine vein on both sides was bypassed and measured. A four-way stopcock was placed distal to the flow sensor in the circuit with a catheter attached to its side arm to measure the respective venous pressures when flow was uninterrupted. Facial venous pressure was measured when the tap of the stopcock was placed in the upstream direction. Measurement of nasal airway resistance Since the nasal cavity is basically made up of a bony structure lined by a layer of profusely vascular mucosa, nasal airway resistance would be affected by vascular capacitance, transcapillary fluid movement and mucosal secretion. Transcapillary fluid movement is a slow process (Mellander & Johnansson, 1968) therefore, if present during the short-term observation periods associated with nerve stimulation, its effect must have been comparatively small. Mucosal secretion does occur with electrical stimulation of the nerve of pterygoid canal (Eccles & Wilson, 1973; Anggard, 1974; Gadlage, Behnke & Jackson, 1975). In order to minimize its influence on nasal airway resistance, the animal was placed in a slightly head-down position to facilitate fluid drainage from the nasal cavity. Nasal airway resistance was assessed as described previously (Lung et al. 1984). Two cuffed endotracheal tubes (5 mm, Portex) were inserted into the posterior nasal choanae via an oesophageal incision. The cuffs were inflated to produce airtight seals. Continuous flows of humidified air, produced by electrical air compressors (Model AC0902, Nitto Kohki Co. Ltd.), were passed through both tubes and hence into the nasal cavities in the direction of expiration. The airflow was humidified by bubbling the air through water at room temperature. The airflow rates were adjusted and measured with rotameters. The pressure difference between each posterior nasal choana and the atmosphere was measured with a differential pressure transducer. Nasal airway resistance was expressed as the ratio of pressure difference (mmH20) to its related airflow (1 min-'). The independence of each airflow system was tested by occluding each nostril and confirming that the pressure on only the appropriate side was increased. All pressure and flow variables were recorded on magnetic tape (Store 14, Racal) and an oscillographic chart-recorder (2800S, Gould) and the mean values were calculated with the use of Gould Universal amplifiers (Model 13-4615-58). Gould P231D transducers were used for arterial pressure measurement, Statham P23B transducers for venous pressure measurement and Gould 124 M.A.LUNG AND J.C.C. WANG PM 5E+0-15-350 transducers for nasal airway pressure measurement. All pressure transducers were zeroed to atmospheric pressure and set at the level of mid-chest. Electromagnetic flow sensors (SP 7515, Statham) were connected to Statham SP2202 flowmeters. Determination of zero baseline and calibration of the sensors were carried out as described previously (Lung & Wang, 1987a). Electrical stimulation of autonomic nerves In the dog, preganglionic parasympathetic fibres to the nose follow the great superficial petrosal nerve and the nerve of the pterygoid canal (or vidian nerve) to relay in the pterygopalatine (or sphenopalatine) ganglion, from which postganglionic fibres are distributed to the nasal mucosa alongside the caudal nasal nerve. The preganglionic sympathetic fibres pass to the cervical vagosympathetic trunk to relay in the superior cervical ganglion, from which some postganglionic

BP 150r (mmHg) 0 I

A, a (mmHg) 150[0

Qd. v Qdv30[ (ml min-1) 10 as 20. (ml min-') 10 1 min Pi,a-w 7 (mmH20) r 6 A A ' A A A 0.5 0*1*2.3*4-5 0.4 0.1 1 ms Fig. 1. Anexperimental recordillustrating thenasal vascularandairway responsestovarying pulse duration (from 01 to 1 ms) of unilateral electrical stimulation of the cervical sympathetic trunk (left side) at 3 V and 25 Hz in a dog with constant-flow vascular perfusion of the nasal mucosa. Traces from above downwards: BP, systemic arterial pressure. P,,a left nasal arterial perfusion pressure. Qd,,v total dorsal nasal venous outflow. Q8,v total sphenopalatine venous outflow. P left nasal airway pressure. Arrow, electrical stimulation at different pulse duration. Bar, the period of stimulation. fibres form the deep petrosal nerve which joins the nerve of pterygoid canal and passes through the pterygopalatine ganglion without any relay and is finally distributed to the nasal mucosa alongside the caudal nasal nerve; other postganglionic fibres may reach the nasal mucosa via the caudal nasal (or sphenopalatine) and the major palatine divisions of the maxillary nerve (Miller, Christensen & Evans, 1964). In order to study the autonomic nervous control on the nasal vasculature, the cervical sympathetic trunk just cranial to the caudal cervical ganglion, the caudal nasal nerve, the major palatine nerve and the nerve ofpterygoid canal were exposed as described previously (Lung & Wang, 1986). The cut peripheral ends of these nerves were stimulated separately by bipolar platinum electrodes. Square-wave impulses were delivered from a Grass S4 stimulator through an isolation unit (SI U4). Since the aim of this study was to investigate the nasal responses to the actions of two groups of autonomic nerves, it seemed more appropriate to carry out electrical stimulation at varying voltage at supramaximal frequency and pulse duration. Stimulation frequencies ranging from 10 to 30 Hz and pulse durations from 0 1 to 1-5 ms were tested at different voltages and maximal responses were obtained at frequencies of 20-25 Hz and pulse durations of 08-10 ms (Fig. 1). Hence, in all subsequent experiments, electrical stimulation was performed with varying voltage at the fixed supramaximal frequency of 25 Hz and pulse duration of 1 ms for a period of 30-60 s. AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 125

Drugs Ganglionic blockade was induced with hexamethonium bromide, 10 mg (Sigma), adrenergic neurone blockade with bretylium tosylate, 10 mg (Wellcome Foundation), ,1-adrenoreceptor blockade with propranolol hydrochloride, 0-5 mg (Sigma), a-adrenoreceptor blockade with phentolamine mesylate, 1 mg (Ciba-Geigy) and cholinergic blockade with atropine sulphate, 0 5 mg (Merck). Blockade was induced with the agent administered slowly in 01 ml saline intra-arterially (I.A.) via the perfusion circuit. The adequacy of various blockades was confirmed by inhibition of nasal vascular and airway responses to reflexes or drug injections; ganglionic and adrenergic neurone blockades were tested by arterial chemoreceptor stimulation (Lung & Wang, 1986); f,- adrenoreceptor blockade by salbutamol 1 ,ug, I.A. (Glaxo); a-adrenoreceptor blockade by phenylephrine hydrochloride, 0 5 ,ug, I.A. (Sigma); and cholinergic blockade by methacholine chloride, 1 ,ug, I.A. (Sigma). The nasal responses to these drugs have been described (Lung et al. 1984). Doses were expressed as the weight of the salt. The results were given as means+ S.E. of the means. The Student's t test was used to determine the level of significance of differences between the means.

RESULTS Effects of stimulation of the cervical sympathetic trunk, major palatine nerve or caudal nasal nerve With stimulation of the cervical sympathetic trunk, the average voltage for initiating an airway resistance response was 2X5 V and that for a vascular resistance response was 3-0 V; maximal airway response occurred at 4 V and maximal vascular resistance response at 5 V (Figs 2 A and 3A). However, electrical stimulation of the caudal nasal and the major palatine nerves required a higher average voltage for initiating both airway and vascular responses: 5 V for an airway response and 10 V for a vascular resistance response. The voltage for inducing maximal airway and vascular resistance responses was also comparatively higher, about 15-20 V respectively. Unilateral stimulation of either the cervical sympathetic trunk, major palatine nerve or caudal nasal nerve caused an increase in vascular resistance and a decrease in airway resistance (Fig. 2A). Both venous outflows showed an initial transient increase at about 1-5 s followed by no change or a decrease in outflow (Fig. 3A). The magnitude of all airway and vascular responses was in direct proportion to the intensity of stimulation. The contralateral vascular and airway resistances showed similar changes, about 5-10% of the ipsilateral responses (Fig. 4). However, in five out of twenty dogs, the contralateral airway resistance did not respond to unilateral sympathetic stimulation. Electrical stimulation of the cervical sympathetic trunk sometimes caused a slight increase in respiratory rate (Fig. 4). This is most probably due to a slight contamination with vagal afferent fibres. Pharmacological stimulation of the pulmonary stretch receptors and C fibre receptors has been found to result in a decrease in nasal vascular resistance and an increase in nasal airway resistance (Lung & Widdicombe, 1987). Hence, it is unlikely that the nasal responses to stimulation of the cervical sympathetic trunk are due to activation of the vagal afferent fibres. Bretylium (n = 5), an adrenergic neurone blocker, completely abolished all nasal responses to stimulation of the cervical sympathetic trunk, major palatine nerve and 126 M. A. LUNG AND J. C. C. WANG caudal nasal nerve. Propranolol (n = 5), a fl-adrenergic receptor blocker, and atropine (n = 5), a cholinergic muscarinic receptor blocker, had no effect on the responses. Phentolamine, an a-adrenergic receptor blocker, greatly lessened the vascular resistance response but only partially reduced the responses of the airway and the two venous outflows (Fig. 2B and 3B).

A 80 n =20

-40

-20

-40

B "~, 20

-0 -20 *t~~~~~~~ -40 2 3 4 5 Stimulation (V) Fig. 2. Actions of cervical sympathetic nervous stimulation (25 Hz and 1 ms) on nasal vascular (stippled histograms) and airway (hatched histograms) resistances in dogs with constant-flow vascular perfusion of nasal mucosa. A, normal dogs; B, dogs with phentolamine. Values, expressed as percentage of control change (% A), are means+ S.E. of the mean. n indicates number of animals. *P < 005, when compared to the corresponding control. tP < 005, when compared to normal dogs.

Effects of stimulation of the nerve of pterygoid canal (vidian nerve) The average voltage for initiating vascular and airway responses to stimulation of the nerve of pterygoid canal was 5 V and that for maximal responses was 20 V. Unilateral stimulation of the nerve of pterygoid canal decreased nasal vascular resistance with the magnitude of the response in direct proportion to the voltage given. However, the airway response was biphasic; an increase in airway resistance to low-voltage (below 10 V) stimulation and a decrease in airway resistance to high- voltage (above 10 V) stimulation (Figs 5A and 7). The contralateral airway resistance rarely responded whereas vascular resistance showed a similar change, about 5-10 % of the ipsilateral response (Fig. 7). The response of the two venous AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 127 outflows also depended on the voltage given. Low-voltage stimulation decreased dorsal nasal venous outflow but increased sphenopalatine venous outflow. High- voltage stimulation caused only a slight increase in sphenopalatine venous outflow but an initial transient increase followed by a decrease in dorsal nasal venous outflow (Figs 6A and 7). After hexamethonium, a ganglionic blocker which was administered intra- arterially so as to cause blockade of the parasympathetic ganglia supplying the nasal

Qd, Qs, v I A 20' n= 20 *

u r = -10 *

BP 150O (mmHg) 0 Fi a 200r (mmHg) 50 [

(mmH2O) 6 Pr, a 150[ (mmHg) 50 Pr, a-w 8t (mmH2O) 6

(ml min-1) 20 as, 20E (ml min-1) 10 1 mi

Fig. 4. An experimental record illustrating the bilateral nasal vascular and airway responses to unilateral electrical stimulation of the cervical sympathetic trunk (left side) at 3 V, 25 Hz and 1 ms pulse duration in a dog with constant-flow vascular perfusion of the nasal mucosa. Traces from above downwards: BP, systemic arterial pressure. PIa, left nasal arterial perfusion pressure. Pl,..w, left nasal airway pressure. Pras right nasal arterial perfusion pressure. Pra.-w' right nasal airway pressure. Qd , total dorsal nasal venous outflow. Q.. v total sphenopalatine venous outflow. V, pneumotachograph tracing. Bar, electrical stimulation.

Effects of combined stimulation of the cervical sympathetic trunk and the nerve of pterygoid canal We studied the effects of combined stimulation of the cervical sympathetic trunk at a voltage (4 V) which caused the maximal increase in vascular resistance and decrease in airway resistance and the nerve of the pterygoid canal at a voltage (7 5 V) which caused the maximal opposite pattern of response, i.e. a decrease in vascular resistance and an increase in airway resistance. After induction of a sustained increase in vascular resistance and decrease in airway resistance by sympathetic stimulation, additional stimulation of the nerve of pterygoid canal returned the vascular resistance close to but still above the prestimulated control level and airway resistance remained significantly reduced. Withdrawal of sympathetic stimulation, A UTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 129 under continuous stimulation of the nerve of pterygoid canal, could only return the vascular resistance to prestimulation control level and the airway resistance still remained very low as with sympathetic stimulation. Subsequent sympathetic stimulation was able to increase vascular resistance again but had no further effect on airway resistance (Fig. 8).

A 20 n =25 * .T- 1-A_ 1- 1A.. 1 IA

* -30 * B 20 n = 5

o -30 L C uacn 'n ._ cs Or-

-301 D 20 n = 5 ...6t *t N..t IN- I.-. I-. 1.- -301 *t * t

U 5 10 15 Stimulation (V) Fig. 5. Actions of stimulation of the nerve of pterygoid canal (25 Hz and 1 ms) on nasal vascular (stippled histograms) and airway (hatched histograms) resistances in dogs with constant-flow vascular perfusion of the nasal mucosa. A, normal dogs; B, dogs with phentolamine; C, dogs with bretylium; D, dogs with hexamethonium. Values, expressed as percentage of control (% A), are means+ S.E. of the mean. n indicates number of animals. *P < 005, when compared to corresponding control. tP < 0 05, when compared to normal dogs.

Effects of surgical denervations and pharmacological blockades (Table 1) Section of caudal nasal nerve, major palatine nerve or cervical sympathetic trunk decreased vascular resistance and increased airway resistance and the two venous outflows. Additional pharmacological treatment with either adrenergic receptor blockers (propranolol or phentolamine), or a cholinergic receptor blocker (atropine), did not induce further changes in all measured vascular and airway variables. However, additional treatment with bretylium, an adrenergic neurone blocker, abolished all vascular and airway changes, returning the variables to near predenervation levels (see Discussion). Sectioning the nerve ofpterygoid canal, and additional pharmacological treatment 5 PHY 419 130 -M.A.LUNG AND J.C.C. WANG by parasympathetic kanglionic blocker (hexamethonium), or by /3-adrenergic receptors and cholinergic receptor blockers (propranolol and atropine), had no effect on all measured vascular and airway variables. Additional treatment with an a- adrenergic receptor blocker (phentolamine) resulted in a decrease in vascular resistance but increases in airway resistance and venous outflows. But, additional

Qd, v Os. v A 15 n=255 *LIn ** ** -15. B 15 n= 5 *

- 8 -15... a** ** C -n1

D15.- mm* n D 1 n = 5 O * * * *t *t*t 4 * * *

m t t t *t *t **

0 5 10 15 0 5 10 15 Stimulation (V)

Fig. 6. Actions of stimulation of nerve ofpterygoid nerve (25 Hz and 1 ms) on total dorsal nasal venous outflow (Qd,V) and total sphenopalatine venous outflow (Q.) in dogs with constant-flow vascular perfusion of nasal mucosa. A, normal dogs; B, dogs with phentolamine; C, dogs with bretylium; D, dogs with hexamethonium. Filled histograms, initial transient response at 1-5 s. Open histograms, late steady response. Values, expressed as percentage of control change (% A), are means + S.E. of the mean. n indicates number of animals. *P < 0 05, when compared to corresponding control. tP < 0.05, when compared to normal dogs. treatment with bretylium, an adrenergic neurone blocker, caused an increase in vascular resistance but decreases in airway resistance and the two venous outflows (see Discussion).

DISCUSSION

In this study, we have made direct and simultaneous measurement of nasal airway and vascular resistances and also, for the first time, vascular capacitance via changes in total venous outflow as well as relative distribution of blood flow in the AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATUJRE 131 anterior and posterior venous systems. The two nasal venous systems have been shown to be functionally and anatomically separate (Lung & Wang, 1987a, 1989) and their response to any experimental intervention may be different. All pharmacological agents were given in minimal effective doses intra-arterially so as to limit their actions locally to the nasal mucosa without inducing secondary effects due to the systemic responses of the agents if administered intravenously.

A B BP 150 ------_- (mmHg) 50

R, a 150[ _L

(mmH2O) 4

Pr, a 150r (mmHg) 50

Pr, a-w 9r (mmH2O) 6

30 Qd, (ml min-1) 20

Qsv 20 (ml min-') 101

Fig. 7. An experimental record illustrating the bilateral nasal vascular and airway responses to unilateral electrical stimulation of the nerve of pterygoid canal (left side, 25 Hz and 1 ms) at low and high voltages in a dog with constant-flow vascular perfusion of nasal mucosa. A, stimulation with low voltage, 5 V. B stimulation with high voltage,

15 V. Traces from above downwards: BP, systemic arterial pressure. PI, . left nasal arterial perfusion pressure. PI,a, left nasal airway pressure. Pr a, right nasal arterial perfusion pressure. Pr a-w, right nasal airway pressure. Qd,v total dorsal nasal venous outflow. Qs,v total sphenopalatine venous outflow. V, pneumotachograph tracing. Bar, electrical stimulation.

Sympathetic influence We have found that sympathetic nervous stimulation via stimulation of the cervical sympathetic trunk increases nasal vascular resistance and decreases nasal airway resistance suggesting constriction of both resistance and capacitance vessels of the nasal vascular bed. The threshold voltage for a nasal airway resistance response is lower than that for a nasal vascular resistance response indicating that the capacitance vessels are either comparatively more sensitive to or under more

5-2 132 M.A.LUNG AND J.UC.C WANG

BP 150E (mmHg) 50 8 Al a-w (mmH20) 4

P a (mmHg) 1001

Qd, v (ml min-1)

Pd, v (mmHg) 20 Os, v 10 (ml min-1) Ps,v 101 (mmHg) 0 1 min L LL IL JI I I LJL, JL4J,L Fig. 8. An experimental record illustrating the nasal vascular and airway responses to combined electrical stimulation of the cervical sympathetic trunk (4 V, 25 Hz and 1 ms) and the nerve of pterygoid canal (7 5 V, 25 Hz and 1 ms) on the left side in a dog with constant-flow vascular perfusion of the nasal mucosa. Traces from above downwards: BP, systemic arterial pressure. P,a-w left nasal airway pressure. P15, left nasal arterial perfusion pressure. Qd,v total dorsal nasal venous outflow. Pd, dorsal nasal venous pressure. Q,v, total sphenopalatine venous outflow. P. v, sphenopalatine venous pressure. V, pneumotachograph tracing. Thick bar, stimulation of the cervical sympathetic trunk. Thin bar, stimulation of the nerve of pterygoid canal.

TABLE 1. Actions of sympathetic and parasympathetic surgical denervations and pharmacological ganglionic, neuronal and receptor blockades on nasal vascular resistance (R,), nasal airway resistance (R.-W), dorsal nasal venous flow (Qdv), and sphenopalatine venous flow (Q.,,) in dogs with constant-flow vascular perfusion of nasal mucosa

RV Ra_w Qd,v Qs, v Change Change Change Change n (% control) (% control) (% control) (% control) Section of caudal nasal nerve 6 -15 + 3.7* + 20+3-2* + 15±3.3* + 10+2.8* Section of major palatine nerve 6 -8+2-8* + 10 + 2-6* +9±2-9* +7±+22* Section of cervical sympathetic 20 -18 + 1-8* + 25 + 1.9* + 25+ 2.0* +17+1.8* trunk + bretylium (IO mg) 5 +5±341 +5+3-3 -8+3-0 -3+2-5 +propranolol (0-5 mg) 5 -15+2.7* +20+3.0* +21±3.9* + 14+3.6* + phentolamine (1 mg) 5 -22 + 3.2* +28+3.5* +24±3-3* + 16 ±3.0* +atropine (0-5 mg) 5 -20 + 2.9* +21 +2.5* +28+3.7* + 15±3-4* Section of nerve of pterygoid 25 -5+2-5 +3+1-9 +5+2-6 +4+2-3 canal + hexamethonium (10 mg) 5 +4+2-0 -4-2+2-2 -3+2-4 -5+2-6 + bretylium (10 mg) 5 + 15± 3.4* - 18+ 3.3* - 18+3-8* - 15+3-5* + propranolol (0-5 mg) 5 -2+1*5 +3+1-8 +3+2-1 +5+2-5 +phentolamine (1 mg) 5 -14+ 30* + 10 + 2.8* +20+3-9* + 13 ±3-7* + atropine (0 5 mg) 5 -6 + 2-8 +5+2-4 +3+2±4 +4+2-5 Values are means +s.E. of the mean. n = number of animals. Control values: RV_ 7.3+0-22 mmHg ml-' min (n = 57); Ra, 3-2+0012 mmH2O 1'- min-' (n = 57); Qd,v, 28±0X7 ml min-' (n = 57); and Q,v, 9+0-5 ml min-' (n = 57). *P < 005, when compared with control. All drugs were given intra-arterially so as to limit their actions locally to the nasal mucosa. AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 133 prominent control from the sympathetic nervous system than the resistance vessels. Such a physiological finding is supported by the anatomical observation that, in contrast to the sparse adrenergic innervation of the veins of skeletal muscles and other tissues of the body, the veins within the nasal mucosa are surrounded by very rich adrenergic plexuses (Dahlstrom & Fuxe, 1965). Both dorsal nasal and sphenopalatine venous outflows show an initial transient increase followed by no change or a decrease in flow. The initial transient response suggests a decrease in vascular capacitance in both anterior and posterior venous systems via constriction of the capacitance vessels whereas the late decrease in flow, since this is coupled with a striking decrease in nasal airway resistance, may indicate that vasoconstriction has been so intense in the two main venous systems that there is a shift of blood flow through other minor pathways, such as the palatine plexus or veins of the underlying bony cavity, which may be under less sympathetic influence. Bretylium has been found to abolish all nasal vascular and airway responses to sympathetic stimulation showing that the responses are due to activation of the efferent adrenergic nerve fibres to the nasal mucosa. Propranolol and atropine have no effect on any of these responses while phentolamine has been found to decrease greatly the vascular resistance response but only partially weakens the airway resistance as well as the venous outflow response. Hence, the vascular resistance response and a small part of the vascular capacitance or nasal airway response are mediated via the a-adrenergic receptors whereas most of the vascular capacitance or nasal airway response is mediated via some non-cholinergic and non-adrenergic mechanism(s). Neuropeptide Y has been found to co-exist with noradrenaline in sympathetic neurones supplying the nasal mucosa; however, these neurones have been identified surrounding mainly arteries and arterioles (Lundberg, Terenius, Hokfelt, Martling, Tatemoto, Mutt, Polak, Bloom & Goldstein, 1982). Ichimura, Mineda & Seki (1988) recently demonstrated in vitro that although neuropeptide Y contracts a nasal mucosal strip (which mostly comprises capacitance vessels) under resting tension, it relaxes the electrically induced contraction of the strip. Therefore, the question whether or not neuropeptide Y is responsible for non-cholinergic and non-adrenergic sympathetic constriction of the nasal capacitance vessels still awaits further investigation. We cannot rule out the possibility that the response may be due to the action of other co-transmitters which have not yet been identified in the sympathetic nerves supplying the nasal mucosa. Serotonin, ATP and other neuropeptides have been found to co-exist with noradrenaline in many peripheral sympathetic ganglia and neurones (Burnstock, 1981). Rooker & Jackson (1969) and Asakura, Hoki, Kataura, Kasaba & Aoki (1985), by measuring changes in nasal airway resistance or intranasal balloon pressure after sectioning the cervical sympathetic nerve or administering a ganglionic agent, presented indirect evidence of basal sympathetic tone in canine nasal mucosa. We have found that nasal vascular resistance decreases and nasal airway resistance as well as venous outflows increase after surgical sympathetic denervation, dem- onstrating a background sympathetic discharge to both resistance and capacitance vessels. However, bretylium treatment after surgical denervation has been found to return vascular and airway resistances to near pre-denervation control levels indicating that the agent induces an increase in vascular resistance but a decrease in airway resistance. This is probably due to the action of bretylium on adrenergic 134 M. A. LUNG AND J. C C. WANG endings causing the release of noradrenaline and hence vasoconstriction of the nasal blood vessels (Weiner, 1980). According to the textbook on the anatomy of the dog, the caudal nasal and the major palatine nerves carry sensory nerve fibres as well as sympathetic nerves (Miller et al. 1964). We have found that the nasal vascular and airway responses to electrical stimulation or surgical denervation of these nerves are similar to those with cervical sympathetic stimulation or denervation; also the magnitude of the nasal responses to caudal nasal nerve stimulation almost doubles that of responses to stimulation of the major palatine nerve. Hence, both nerves carry mainly sympathetic fibres with a negligible number of sensory fibres and, with about two- thirds of the postganglionic sympathetic fibres, innervate nasal mucosa via the caudal nasal nerve and less than one-third via the major palatine nerve. Bilateral increase in nasal patency has been reported in cats and dogs on unilateral cervical sympathetic stimulation (Franke, 1966; Malm, 1973; Wilson & Yates, 1978). We have found that unilateral sympathetic stimulation definitely causes constriction of the contralateral resistance vessels whereas the capacitance vessels may or may not respond. Hence the response of the contralateral nasal airway in previous studies is due primarily to the change in blood flow via dilatation of resistance vessels rather than to active dilatation of the capacitance vessels. Parasympathetic influence We have found that stimulation of the nerve of pterygoid canal decreases nasal vascular resistance at all levels of stimulation. The response of capacitance depends on the intensity of stimulation; low-voltage stimulation increases vascular capacitance as nasal airway resistance increases and total venous outflow (i.e. the sum of dorsal nasal and sphenopalatine venous outflows) decreases whereas high- voltage stimulation decreases vascular capacitance as nasal airway resistance decreases and total venous outflow increases. However, the distribution of blood flow in the two venous systems is different at the two levels of stimulation. It must be stressed that in our constant-flow vascular perfusion experiments, the same total flow would be distributed through all vascular channels per unit time. Hence, if more blood flows through one vascular channel, this will result in less blood flowing to other channels. Low-voltage stimulation increases sphenopalatine venous blood flow but decreases dorsal nasal venous blood flow. This means that relatively more blood flows into the posterior venous system than into the anterior venous system. Hence the increase in nasal airway resistance to low-voltage stimulation is probably more related to an increase in vascular capacitance of the posterior venous system rather than due to the change in capacitance of the anterior venous system. High-voltage stimulation causes a smaller increase in sphenopalatine venous blood flow but an initial transient increase followed by a decrease in dorsal nasal venous blood flow. The results indicate two points. Firstly, there is still relatively more blood flowing into the posterior venous system, although to a lesser extent. Secondly, there is a decrease in capacitance of the anterior venous system as a result of the squeezing effect of strong vasoconstriction. Hence the decrease in nasal airway resistance to high-voltage stimulation is probably related to a decrease in the vascular capacitance of the anterior venous system rather than due to the change in capacitance of the AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 135 posterior venous system. The above findings suggest that, if the strength of stimulation is low, both resistance vessels and vessels of the posterior venous system dilated but, if the strength of stimulation is high, besides dilatation of resistance vessels and vessels of the posterior venous system, constriction of the vessels of the anterior venous system will occur. Similar biphasic nasal airway resistance response to vidian nerve stimulation has been reported in the cat (Malcomson, 1959; Malm, 1973; Eccles & Wilson, 1974); however, Gadlage & co-workers (1975) could only demonstrate an increase in nasal airway resistance in the dog. The highest level of stimulation used by Gadlage et al. was 10 V and we have shown that the decrease in nasal airway resistance is elicited in the dog only when the strength of stimulation is higher than 10 V. Parasympathetic ganglionic blockade by hexamethonium reverses and sympathetic noradrenergic neurone and receptor blockades by bretylium and phentolamine respectively both enhance the nasal vascular resistance response to stimulation of the nerve of pterygoid canal. These findings suggest that, since the nerve of pterygoid canal carries both sympathetic and parasympathetic fibres, the vasoconstriction of the resistance vessels after hexamethonium is due to activation of the sympathetic fibres whereas the vasodilatation of the resistance vessels is due to activation of the parasympathetic fibres; however, when the whole nerve trunk is stimulated the parasympathetic vasodilatory response is predominant. After parasympathetic ganglionic blockade by hexamethonium, the increase in nasal airway resistance to stimulation of the nerve of pterygoid canal is completely abolished and the nasal airway shows a decrease in airway resistance at all levels of stimulation, coupled with a transient increase in both venous outflows, suggesting a decrease in vascular capacitance or vasoconstriction in both venous systems. After sympathetic noradrenergic neurone and receptor blockades by bretylium and phentolamine respectively, the decrease in nasal airway resistance to high-voltage stimulation ofthe nerve ofpterygoid canal is abolished and the nasal airway response at all levels of stimulation is an increase in airway resistance, suggesting an increase in vascular capacitance. After bretylium, the biphasic dorsal nasal venous outflow response is abolished, being replaced by a steady decrease in flow and coupled with a bigger increase in sphenopalatine venous outflow. This suggests an increase in vascular capacitance in the posterior venous system and an abolition of vasoconstriction in the anterior venous system. After phentolamine, the biphasic dorsal nasal venous outflow is alleviated but not abolished, suggesting that the vasoconstriction of the anterior venous system is mediated partly via a-adrenergic receptors and partly via some non-adrenergic mechanism(s). Hence, low-voltage stimulation of the nerve of pterygoid canal causes predominantly parasympathetic dilatation of the capacitance vessels (in the posterior venous system) whereas high- voltage stimulation of the nerve causes predominantly sympathetic adrenergic constriction of the capacitance vessels with part of the response occurring via the a-adrenergic receptors (in the anterior venous system). Recently, Jackson and his co-workers (Jackson & Steele, 1985; Wang & Jackson, 1988) introduce the concept that the parasympathetic nasal vasodilatation is not due to a direct action on the nasal blood vessels but occurs by means of an inhibition of the noradrenaline release from the adrenergic neurones. Cholinergic inhibition of 136 M. A. LUNG AND J. C. C. WANG adrenergic transmission is atropine-sensitive (Vanhoutte, 1977). We have found that the vasodilatory response to stimulation of the pterygoid canal nerve is not blocked by atropine. This is in agreement with the finding of other workers that the nasal airway response to similar nerve stimulations, in both cats and dogs, is atropine- resistant (Malcolmson, 1959; Malm, 1973; Eccles & Wilson, 1974; Gadlage et al. 1975). We have also shown that adrenergic neurone and receptor blockades result in enhancement rather than inhibition of the parasympathetic vasodilatory response. Hence, it seems unlikely that cholinergic inhibition of adrenergic transmission is important in parasympathetic nasal vasodilatation. Vasoactive intestinal peptide (VIP) has been identified in the sphenopalatine ganglia and nerves supplying glands and small blood vessels of the cat nasal mucosa (Uddman, Alumets, Densert, Hakanson & Sundler, 1978; Lundberg, Anggard, Emson & Hokfelt, 1981). In the dog with constant-flow vascular perfusion of the nasal mucosa, VIP greatly decreases nasal vascular resistance with little effect on nasal airway resistance suggesting a strong dilatatory action on the resistance vessels but not on the capacitance vessels (Lung et al. 1984). In the cat, VIP increases the spontaneous sphenopalatine venous outflow as well as nasal airway resistance (Malm, Sundler & Uddman, 1980). The increase in nasal airway resistance as a result of VIP in feline experiments is probably not due to active dilatation of capacitance vessels but rather the passive effect of an increase in spontaneous blood flow as a result of dilatation of resistance vessels. Although the level of VIP in the nasal venous blood has been found to increase during stimulation of the nerve of pterygoid canal in the cat (Uddman, Malm, Fahrenkrug & Sundler, 1981), whether or not it is responsible for the atropine- resistant vasodilatation of both resistant and capacitance vessels to similar nerve stimulation still requires further investigation. There is now growing evidence that other neuropeptides co-exist with acetylcholine in the parasympathetic nerves supplying the nasal mucosa (Raphael, Meredith, Baraniuk & Kaliner, 1988). Sectioning the nerve of pterygoid canal does not induce appreciable changes in all measured nasal vascular and airway variables, indicating firstly that there is no background parasympathetic discharge to the nasal mucosa and secondly that either there is no tonic sympathetic discharge via the nerve or there is only a small number of sympathetic fibres in the nerve. Asakura et al. (1985) also reported that the denervation effects on the nasal airway are more prominent after cervical sympathectomy than after vidian nerve sectioning. Hence, under normal conditions, both resistance and capacitance vessels of the nasal mucosa are under the tonic control of the sympathetic nervous system via the caudal nasal and major palatine nerves rather than that of the parasympathetic system via the nerve of pterygoid canal. Unilateral stimulation of the nerve of pterygoid canal in cats has been reported to increase in bilateral nasal patency (Wilson & Yates, 1978). We have found that unilateral stimulation of the nerve ofpterygoid canal seldom causes any change in the contralateral nasal airway but the contralateral resistance vessels always respond by dilatation. Hence, in the dog, there may only be a crossing-over of parasympathetic influence to contralateral resistance vessels but not to capacitance vessels as in the cat. AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 137

Interaction between sympathetic and parasympathetic influence Figure 8 illustrates the interaction between the sympathetic and parasympathetic control of the nasal blood vessels. Under continuous optimal sympathetic influence, the constriction of the resistance vessels can be alleviated by additional optimal parasympathetic discharge but not that of the capacitance vessels. Withdrawal of sympathetic influence with continuation of parasympathetic discharge further alleviates the constriction of the resistance vessels; however, the tone of the capacitance vessels remains unchanged as with sympathetic stimulation. These findings indicate that when both divisions of the autonomic nervous, system discharge optimally and simultaneously, the nasal responses are predominantly sympathetic, especially those of the capacitance vessels or nasal airway. Patients with nasal rhinitis show signs of mucosal congestion and nasal airway obstruction. The symptoms are believed to be due to a disturbance in autonomic nervous activity resulting in parasympathetic dilatation of nasal blood vessels and surgical interruption of the parasympathetic nerves (vidian neurectomy) is sometimes used as a therapeutic treatment (Golding-Wood, 1961). Such a therapy could alleviate the symptoms to a certain extent in some subjects. However, in many cases, vidian neurectomy has been found to result in further nasal obstruction (Proctor & Adams, 1976). Results of the present study demonstrate that the nasal blood vessels, and in particular the capacitance vessels, are under predominantly sympathetic control, and hence it seems likely that the key mechanism for mucosal congestion is a withdrawal of sympathetic discharge rather than an overactivity of the parasympathetic system. Of course the two mechanisms may operate simultaneously in causing mucosal congestion in nasal rhinitis.

This work was supported by the Croucher Foundation.

REFERENCES ANGGARD, A. (1974). The effects of parasympathetic nerve stimulation on the microcirculation and secretion in the nasal mucosa of the cat. Acta oto-laryngologica 78, 98-105. ANGGARD, A. & EDWALL, L. (1974). The effects of sympathetic nerve stimulation on the tracer disappearance rate and local blood content in the nasal mucosa of the cat. Acta oto-laryngologica 77, 131-139. ASAKURA, K., HOKI, K., KATAURA, A., KASABA, T. & AOKI, M. (1985). Control of nasal mucosa by the tonic activities of the autonomic nervous systems in dogs. Acta oto-laryngologica 100, 450-455. BURNSTOCK, G. (1981). Review lecture. Neurotransmitters and trophic factors in the autonomic nervous system. Journal of Physiology 313, 1-35. DAHLSTROM, A. & FUXE, K. (1965). The adrenergic innervation of the nasal mucosa of certain mammals. Acta oto-laryngologica 59, 65-72. EcCLES, R. & WILSON, H. (1973). The parasympathetic secretory nerves of the nose of the cat. Journal of Physiology 230, 213-223. EcCLES, R. & WILSON, H. (1974). The autonomic innervation of the nasal blood vessels of the cat. Journal of Physiology 238, 549-560. FRANKE, F. E. (1966). Sympathetic control ofthe dog's nasal blood vessels. Proceedings ofthe Society for Experimental Biology and Medicine 123, 544-547. 138 M. A. LUNG AND J. C. C. WANG

GADLAGE, R., BEHNKE, E. E. & JACKSON, R. T. (1975). Is the vidian nerve cholinergic? Archives of Otolaryngology 101, 422-425. GOLDING-WOOD, P. H. (1961). Observations on petrosal and vidian neurectomy in chronic vasomotor rhinitis. Journal of Laryngology and Otology 75, 232-247. ICHIMURA, K., MINEDA, H. & SEKI, A. (1988). Vascular effects of neuropeptides on nasal mucosa. Annals of Otology, Rhinology, and Laryngology 97, 289-293. JACKSON, R. T. & ROOKER, D. W. (1971). Stimulation and section of the vidian nerve in relation to autonomic control of the nasal vasculature. Laryngoscope 81, 565-569. JACKSON, R. T. & STEEL, R. W. (1985). The inhibition of norepinephrine release in nasal mucosa by acetylcholine. Rhinology 23, 59-64. LUNDBERG, J. M., ANGGARD, A., EMSON, P. & HOKEFELT, T. (1981). Vasoactive intestinal polypeptide and cholinergic mechanisms in cat nasal mucosa: Studies on choline acetyl- transferase and release of vasoactive intestinal polypeptide. Proceedings of the National Academy of Science of the USA 78, 5255-5259. LUNDBERG, J. M., TERENIUS, L., HOKFELT, T., MARTLING, C. R., TATEMOTO, K., MUTT, V., POLAK, J., BLOOM, S. & GOLDSTEIN, M. (1982). Neuropeptide Y (NPY)-like immunoreactivity in peripheral noradrenergic neurons and effects of NPY on sympathetic function. Acta physiologica scandinavica 116, 477-480. LUNG, M. A., PHIPPs, R. J., WANG, J. C. C. & WIDDICOMBE, J. G. (1984). Control of nasal vasculature and airflow resistance in the dog. Journal of Physiology 349, 535-551. LUNG, M. A. & WANG, J. C. C. (1986). Effects of hypercapnia and hypoxia on nasal vasculature and airflow resistance in the anaesthetized dog. Journal of Physiology 373, 261-275. LUNG, M. A. & WANG, J. C. C. (1987 a). Arterial supply, venous drainage and collateral circulation in the nose of the anaesthetized dog. Journal of Physiology 391, 57-70. LUNG, M. A. & WANG, J. C. C. (1987b). Nasal airway response to mucosal perfusion and outflow resistance in the dog and rat. Acta oto-laryngologica 104, 526-532. LUNG, M. A. & WANG, J. C. C. (1987c). Autonomic nervous stimulation on canine nasal vascular and airway resistances. Journal of Physiology 394, 61P. LUNG, M. A. & WANG, J. C. C. (1989). An anatomical investigation of nasal venous vascular bed in the dog. Journal of Anatomy (in the Press). LUNG, M. A. & WIDDICOMBE, J. G. (1987). Lung reflexes and nasal vascular resistance in the anaesthetized dog. Journal of Physiology 386, 465-474. MALCOLMSON, K. G. (1959). The vasomotor activities of the nasal mucous membrane. Journal of Laryngology and Otology 73, 73-98. MALM, L. (1973). Stimulation of sympathetic nerve fibers to the nose of the cat. Acta oto- laryngologica 75, 519-526. MALM, L., SUNDLER,F. & UDDMAN, R. (1980). Effects of vasoactive intestinal polypeptide (VIP) on resistance and capacitance vessels in the nasal mucosa. Acta oto-laryngologica 90, 304-308. MELLANDER, S. & JOHNANSSON, B. (1968). Control of resistance, exchange and capacitance functions in the peripheral circulation. Pharmacological Reviews 20, 117-196. MILLER, M. E., CHRISTENSEN, J. C. & EVANS, H. E. (1964). Anatomy of the dog. Philadelphia, London: W. B. Saunders Company. PROCTOR, D. F. & ADAMS, G. K. (1976). Physiology and pharmacology of nasal function and mucus secretion. Pharmacology and Therapeutics 2, 493-509. RAPHAEL, G. D., MEREDITH, S. D., BARANIUK, J. N. & KALINER, M. A. (1988). Nasal reflexes. American Journal of Rhinology 2,109-116. RoOKER, D. W. & JACKSON, R. T. (1969). The effects of certain drugs, cervical sympathetic stimulation and section on nasal patency. Annals of Otology, Rhinology, and Laryngology 78, 403-415. SLOME, D. (1955). Physiology of nasal circulation. Lectures on the Scientific Basis of Medicine 5, 451-468. TASCHALUSSOW, M. A. (1913). Die Innervation de Gefasse der Nasenschleimhaut. Pfiutgers Archiv 151, 523-542. UDDMAN, R., ALUMETS, J., DENSERT,O., HAKANSON, R. & SUNDLER, F. (1978). Occurrence and distribution of VIP nerves in the nasal mucosa and tracheobronchial wall. Acta oto-laryngologica 86, 443-448. AUTONOMIC NERVOUS CONTROL OF NASAL VASCULATURE 139 UDDMAN, R., MALM, L., FAHRENKRUG, J. & SUNDLER, F. (1981). VIP increases in nasal blood during stimulation of the vidian nerve. Acta oto-laryngologica 91, 135-138. VANHOUTTE, P. M. (1977). Cholinergic inhibition of adrenergic transmission. Federation Proceedings 36, 2444-2449. WANG, H. W. & JACKSON, R. T. (1988). Do cholinergic neurons directly innervate nasal blood vessels? Rhinology 26, 139-146. WEINER, N. (1980). Drugs that inhibit adrenergic nerves and block adrenergic receptors. In The Pharmacological Basis of Therapeutics, ed. GILMAN, A. S., GOODMAN, L. S. & GILMAN, A., pp. 176-210. New York: Macmillan. WILSON, H. & YATES, M. S. (1978). Bilateral nasal vascular responses to unilateral sympathetic stimulation. Acta oto-laryngologica 85, 105-1 10.