The inhibitory action of 5‐hydroxytryptamine on gastric secretory function in rats

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Abstract
1 The inhibitory action of 5-hydroxytryptamine (5-HT) on gastric function was studied in vagotomized rats. 2 5-HT (0.6, 1 or 5 mg kg−1, s.c.) dose-dependently reduced gastric acid secretion evoked by histamine, pentagastrin or methacholine. Pepsin secretion induced by pentagastrin or methacholine was also depressed by 5-HT. 3 Basal secretion of both acid and pepsin was not significantly affected by any of the three 5-HT doses. 4 Indomethacin pretreatment, which significantly decreased gastric mucosal prostaglandin E2 content, did not modify the inhibitory effects of 5-HT on histamine-induced acid secretion, nor did phentolamine or propranolol. 5 This study suggests that 5-HT inhibits gastric secretory function through mechanisms other than by sympathetic influence or increased prostaglandin synthesis. The inhibitory action appears not to be vagus-dependent. Other mechanisms of action are discussed.