5-Hydroxytryptamine stimulates cyclic AMP formation in the tunica muscularis mucosae of the rat oesophagus via 5-HT4 receptors.
The nature of 5-HT4 receptor coupling in the tunica muscularis mucosae of the rat oesophagus has been studied. 5-HT and renzapride stimulated cyclic AMP formation concentration dependently, with -log EC50 values of 7.1 and 6.8, respectively. Renzapride, relative to 5-HT, acted as a partial agonist. Tropisetron (ICS 205 930) and a novel 5-HT4 antagonist, SDZ 205 557, inhibited 5-HT-induced cyclic AMP production competitively, with pA2 estimates of 6.7 and 7.7, respectively. These data are consistent with the hypothesis that 5-HT4 receptors mediate relaxation of the smooth muscle cells of the tunica muscularis mucosae of rat oesophagus via activation of adenylyl cyclase.
Ford
A P
AP
Institute of Pharmacology, Syntex Research, Palo Alto, CA 94304.
Baxter
G S
GS
Eglen
R M
RM
Clarke
D E
DE
D000225:Adenine / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis*; D004947:Esophagus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*
D011985:Receptors, Serotonin; D012701:Serotonin; D000242:Cyclic AMP; D000225:Adenine