5-Hydroxytryptamine stimulates cyclic AMP formation in the tunica muscularis mucosae of the rat oesophagus via 5-HT4 receptors. |
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| Authors: | A P Ford G S Baxter R M Eglen D E Clarke |
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| Affiliation: | Institute of Pharmacology, Syntex Research, Palo Alto, CA 94304. |
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| Abstract: | 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. |
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