5-Hydroxytryptamine-induced secretion by rat jejunum in-vitro involves several 5-hydroxytryptamine receptor subtypes.
The receptors contributing to 5-hydroxytryptamine (5-HT)-induced anion secretion by rat jejunum have been investigated by testing the effects of selective agonists and antagonists in-vitro using both intact and stripped intestinal sheets. In both intact and stripped jejunum 5-HT and 5-methoxytryptamine, an agonist that lacks affinity for 5-HT3 receptors, induced concentration-dependent increases in the short-circuit current (SCC), although 5-methoxytryptamine induced a smaller maximum response. In intact sheets 1-phenylbiguanide, a selective 5-HT3 agonist, induced a response that was similar in magnitude to that of 5-methoxytryptamine, but in stripped preparations it had little effect. Tetrodotoxin inhibited the response of intact jejunum to 5-HT (by 86%) and 5-methoxytryptamine (by 85%) and abolished the response to 1-phenylbiguanide. In stripped sheets inhibition of the 5-HT response by tetrodotoxin was reduced to 27%. Desensitization to 1-phenylbiguanide reduced the response to 5-HT in intact but not stripped sheets whereas, in contrast, desensitization to 5-methoxytryptamine inhibited the 5-HT response in stripped sheets but was without effect in intact sheets. Mianserin, a 5-HT1, 5-HT2 and 5-HT3 antagonist, and renzapride, a 5-HT1 and 5-HT3 antagonist, both reduced the maximum response to 5-HT, but 5-HTP-DP, a 5-HT1 antagonist, was without effect. The 5-HT3 antagonist granisetron reduced the response to 5-HT in intact, but not in stripped sheets. Tropisetron, a 5-HT3 and 5-HT4 antagonist, inhibited the response to 5-methoxytryptamine in both preparations, but did not alter the response to 5-HT. It is concluded that 5-HT-induced jejunal secretion involves more than one 5-HT receptor subtype, with both neural and non-neural mechanisms contributing to the response.
Hardcastle
J
J
Department of Biomedical Science, University of Sheffield, UK.
Hardcastle
P T
PT
D000818:Animals; D004347:Drug Interactions; D007583:Jejunum / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000145:classification / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin