Inhibition of acid secretion in the rat isolated stomach preparation by 5-hydroxytryptamine.

The effect of 5 hydroxytryptamine (5-HT) on gastric acid secretion by the rat isolated stomach has been studied. 5-HT (10 microM) significantly inhibited secretory responses to pentagastrin, histamine and isoprenaline but not those due to bethanechol, dibutyryl cyclic AMP or a phosphodiesterase inhibitor. The response was antagonized by methysergide (25 microM), indomethacin (28 microM) and ibuprofen (240 microM) but not by TTX (1 microM). It is concluded that 5-HT can exert a direct, inhibitory effect on acid secretion by the rat stomach and that this may involve the products of cyclo-oxygenase activity.