The effect of serotonin on pepsin inhibition by duodenal fat.

The purpose of these studies was to evaluate the possible role of serotonin on pepsin secretion. The results of our data suggest that serotonin is a stimulator of pepsin secretion since (a) pretreatment with reserpine (which depletes serotonin stores) abolished the stimulatory effect of histamine on pepsin secretion; (b) pretreatment with UML-491 (a serotonin blocking agent at the effector level) augmented the pepsin inhibition induced by the intraduodenal infusion of fat, and (c) 5-hydroxytryptophan (a serotonin precursor) caused a significant stimulation of pepsin secretion. The mode of action of serotonin is probably by a direct hormonal action on the gastric chief cells.