| Abstract: | The purpose of the present study was to evaluate the effect of serotonin on bethanechol-stimulated gastric acid secretion and antral motility in conscious dogs with gastric fistula. Bethanechol stimulated the acid secretion dose-dependently and maintained the frequency and strength of the antral contractions at a high level. Serotonin inhibited the acid secretion dose-dependently, whereas the antral motility was stimulated. The acid inhibition was blocked by propranolol, and dose-response analysis showed inhibition of a non-competitive type. This study thereby shows that serotonin inhibits bethanechol-stimulated gastric acid secretion similarly to salmefamol (β2-adrenergic agonist)-that is, dose-dependently and non-competitively. Serotonin has been proposed to be a mediator of the β-adrenergic influence on gastric function in vivo, but the counteracting effect of propranolol and the stimulatory effect of serotonin on motility contradict this hypothesis. |
