Is the action of cisapride on the guinea-pig ileum mediated via 5-HT4 receptors?
It has been suggested that benzamides, like cisapride, exert their effects on the guinea-pig ileum via activation of a 5-HT receptor (5-HT4 receptor?) mechanism. The aim of this study was to determine whether an how the 5-HT4 receptor (previously described in mouse colliculi neurones) is involved in the cisapride-induced effect. The effects induced by cisapride were compared with those of 5-hydroxytryptamine (5-HT) and 5-methoxytryptamine (5-MeOT) either alone or in the presence of a 5-HT4 antagonist (micromolar concentration of ICS 205-930) or a benzamide antagonist (R 50 595). As a model we used the electrically stimulated longitudinal muscle myenteric plexus preparation from the guinea-pig ileum. Cisapride (3.10(-7) M), 5-HT and a 5-HT4 receptor agonist 5-MeOT (3.10(-10)-10(-6) M) induced similar effects, i.e. enhancement of the twitch responses. After rinsing the organ baths, a second addition of the agonists resulted in a similar response. The studied agonists showed mutual desensitization. Cisapride desensitized the response induced by 5-HT or 5-MeOT, and 5-MeOT or 5-HT desensitized the effect induced by cisapride. In preparations preincubated with a 5-HT4 receptor antagonist, ICS 205-930- (3.10(-6) M) or R 50 595 (3.10(-7) M), a benzamide with a specific antagonistic action on the effect induced by 5-HT and benzamides on the guinea-pig ileum, the effects induced by cisapride, 5-HT and 5-MeOT were abolished. These results indicate that cisapride indeed exerts its effect via an agonistic action on a serotonin receptor, probably the previously described 5-HT4 receptor.
Meulemans
A L
AL
Department of Gastrointestinal Pharmacology, Janssen Research Foundation, Beerse, Belgium.
Schuurkes
J A
JA
D008735:5-Methoxytryptamine / Q000494:pharmacology*; D000818:Animals; D020117:Cisapride; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology*; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology*; D000077526:Tropisetron
D007211:Indoles; D010880:Piperidines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C065433:R 50595; D012701:Serotonin; D008735:5-Methoxytryptamine; D000077526:Tropisetron; D020117:Cisapride