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SUBMUCOUS REFLEXES ACTIVATED by MUCOSAL STROKING INDUCE CHLORIDE SECRETION in the GUINEA-PIG COLON DISSERTATION Presented In

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SUBMUCOUS REFLEXES ACTIVATED by MUCOSAL STROKING INDUCE CHLORIDE SECRETION in the GUINEA-PIG COLON DISSERTATION Presented In SUBMUCOUS REFLEXES ACTIVATED BY MUCOSAL STROKING INDUCE CHLORIDE SECRETION IN THE GUINEA-PIG COLON DISSERTATION Presented in Partial Fulfillment of the Requirements for the Deqree Doctor of Philosophy in the Graduate School of The Ohio state University By Nanjit s. Sidhu, M.S. The Ohio State University 1 9 9 6 Dissertation Committee: Helen J. Cooke, Ph.D, Advisor Approved by Bruce A. Biagi, Ph.D. Raymond H. Ho, Ph.D. Richard C. Rogers, Ph.D. Robert L. Stephens Jr, Ph.D. Department of Physiology TJMI Number: 9639346 UMI Microform 9639346 Copyright 1996, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 ABSTRACT The type of enteric neurons involved in secretory reflexes activated by stroking the colonic epithelium were unknown. The aim of this study was to identify the neural pathways which mediate stroking-induced epithelial responses in guinea-pig colonic mucosa set up in modified flux chambers. Repetitive stroking of the mucosal surface at 1 stroke/5 min for 90 min in muscle stripped preparation caused a reproducible increase in short-circuit current (Isc) of 87± /xA/cm2 and 87± /iA/cm2 respectively. Tetrodotoxin, (0.25 /xM) completely abolished the Isc response to stroking. The Isc increase was maximally reduced by inhibitors of 5- hydroxytryptamine, 0.1 /iM renzapride and 1 nM 5-HTP-DP, 5- HT1P receptor, but not by 5-HT2, 5-HT3 or 5-HT4 receptor antagonists. Renzapride and tetrodotoxin also significantly reduced the changes in Isc due to exogenous 5- hydroxytryptamine (5-HT) and 5-hydroxyindalpine. The ii stroking responses were reduced by a specific NKX receptor antagonist, GR82334, but not by NK2, or NK3 receptor antagonists. Capsaicin had no effect on stroking responses, ruling out the involvement of capsaicin-sensitive afferents. Atropine, a muscarinic receptor blocker, but not mecamylamine, a nicotinic receptor blocker reduced the secretory responses. Stroking responses were also reduced by VIP (7124) antagonist, and by piroxicam, a cyclooxygenase inhibitor. These results are consistent with the following model. Stroking releases 5-HT from enterochromaffin cells. The released 5-HT activates 5-HT1P receptors on intrinsic afferent neurons causing release of substance P at neuro­ epithelial as well as at the neuro-neuronal junctions. The latter stimulates cholinergic and VIPergic secretomotor neurons in the submucous plexus. Prostaglandins from unknown sources modulate the neural reflex pathways within the submucous plexus. To My Parents iv ACKNOWLEDGMENTS I would like to express my sincere appreciation towards my advisor Doctor Helen J. Cooke for her guidance, insight, instruction, support and the opportunity to pursue my Ph.D. degree at The Ohio State University. I would like to express my thanks to my Advisory Committee members, Doctors Richard C. Rogers, Robert L. Stephens Jr, Bruce A. Biagi, and Raymond H. Ho, for their insight, guidance, advice, suggestions, criticisms, support and help with both my academic and research program during my graduate work. I would like to thank all the faculty members of the Department of Physiology for their help in fulfilling my academic program. My thanks go to Doctor Y.-Z. Wang and Paula Fox for their tremendous help with my research in the lab. I am grateful for the invaluable friendship and help of v Ana R. Chow, Penny W. Burgoon and Chi-Hsiang Chen, and all the graduate students in the Department of Physiology. I also wish to thank those who helped me handle various computer problems, especially Hongwu Chi and Sridhar Varanasi. There is no word which can express my thanks to my parents for their love and foresight in always encouraging me to go one more step higher. VITA 1982-1985.................... Bachelor of Science Gujarat University Ahmedabad, India 1985-1987.................... Master of Science Gujarat University Ahmedabad, India 1987-1990.................... Research Chemist JP Pharmaceutical Company Faridabad, India 1990-1992.................... Graduate Research Associate Uniformed Services University of Health Sciences Bethesda, Maryland, USA. 1992-1994.................... Master of Science, Graduate Research and Teaching Associate, The Ohio State University, Columbus, Ohio, USA. 1994-1996.................... Graduate Research and Teaching Associate, The Ohio State University, Columbus, Ohio, USA. PUBLICATIONS Cooke,H.J., Sidhu,M., Fox,P., Wang,Y.-2., and Zimmerman,E.M.: Substance P as a mediator of colonic secretory reflexes. Under Review, in the American Journal of Physiology. vii Sidhu,M. and Cooke,H.J.: Role for 5-HT and ACh in submucosal reflexes mediating colonic secretion. Am J Physiol. 269 (Gastrointest. Liver Physiol. 32): G346-G351, 1995. Sidhu,M. and Cooke,H.J.: Secretory reflexes triggered by mucosal stroking involve vasoactive intestinal polypeptide. Gastroenterology. 110: A758, 1996. Sidhu,M. and Cooke,H.J.: Multiple signaling messengers in secretory reflexes stimulated by mucosal stroking of guinea- pig colon. Gastroenterology. 108: A1006, 1995. Sidhu,M., Wang.Y.-Z. and Cooke,H.J.: Submucosal reflexes: sensory transduction mechanism and neural pathways influencing mucosal stroking-induced secretion in the guinea-pig colon. Gastroenterology. 106: A1050, 1994. Sidhu,M., Wang,Y.-Z. and Cooke,H.J.: Mucosal stroking stimulates intrinsic, capsaicin-insensitive tachykinin neurons which regulate colonic secretion in guinea-pig colon. Gastroenterology. 106: A1050, 1994. Sidhu,M. and Chinoy,N.J.: Effect of Azadirachta Indica seed extract on testes and accessory sex glands of male mice. Reproductive Biology Journal. Dec, 1987. FIELDS OF STUDY Major Field: Physiology Studies in: Medical Physiology Medical Pharmacology Neuroscience Gastrointestinal Physiology Reproductive Physiology Neurophysiology Cardiovascular Physiology Temperature Regulation Membrane Transport Electronic Instrumentation Statistics Medical Biochemistry viii TABLE OF CONTENTS E ag s Abstract................................................ii Dedication............................................. iv Acknowledgments........................................ v V ita.................................................... vii Table of Contents...................................... ix List of Figures........................................ xii List of Tables......................................... xiv Chapters: I. Introduction........................................ 1 1 Autonomic nervous system........................1 2 Innervation of the mucosa.......................5 3 Neural reflex circuits..........................10 4 Intestinal reflexes............................. 13 5 Neurotransmitters/Neuromodulators.............. 19 i Tachykinins................................19 a Capsaicin............................. 22 b Mechanism of Substance P depletion by Capsaicin.......................... 23 ii Acetylcholine (ACh)...................... 24 iii 5-Hydroxytryptamine (5-HT)................ 27 iv Vasoactive IntestinalPeptide (VIP)....... 31 6 Statement of Research Problem.................. 33 7 Overall aim .................................... 34 II. Methods.............................................37 1 Animals ........................................ 37 2 Tissue Preparations............................ 37 3 Electrical Measurements........................ 38 4 Mucosal Stroking Experiments...................40 5 Strain Gauge Experiments....................... 41 6 5-HT Pulse Experiments......................... 41 7 In Vitro Application of Capsaicin.............. 42 8 Capsaicin Injection Protocol................... 42 9 Statistics..................................... 43 III. Results...........................................44 1 Characteristics of Mucosal Stroking Response....44 2 Effect of Bumetanide and N-Phenylanthranilic Acid (DPC)......................................46 3 Effects of Neural Blockade..................... 46 4 Effect of 5-HT Receptor Antagonists and Agonists........................................47 i 5-HT Antagonists.......................... 47 a Effect of 5-HTlP Receptor Antagonist...47 b Effect of Other 5-HT Receptor Antagonist.......................... 47 ii Effect of 5-HT Receptor Agonists..........48 5 5-HT Pulse Experiments......................... 48 6 Effect of Neurokinin Antagonist and Agonists.... 50 i Effect of Neurokinin Antagonists..........50 a NKX Antagonist....................... 50 b NK2 Antagonist....................... 50 c NK3 Antagonist....................... 51 ii Effect of Neurokinin Agonist..............51 7 Effect of Acute and Chronic Application of Capsaicin....................................51 i Exogenous Application of 10 liM Capsaicin.......................... 51 x ii Capsaicin Injected Animals................ 52 8 Effects of Muscarinic and Nicotinic Blockade.... 53 9 Effects of VIP Antagonists...................... 53 10 Effects of Piroxicam........................... 54 11 Effects of Histamine Blockers.................. 54 12 Experiments with Sequential Addition of Antagonists..................................... 55 i Effect of Piroxicam and 5-HTP-DP........ 55 ii Effect of Piroxicam nad GR82334......... 56 iii Effect of Piroxicam and Atropine........ 57 iv Effect of GR82334 and 5-HTP-DP.......... 57 v Effect of GR82334 and Atropine.......... 58 vi Effect of Atropine and 5-HTP-DP......... 59 vii Effect of 5-HTP-DP, and VIP antagonist (7124)........................ 59 IV. Discussion.........................................
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