The influence of serotonin on insulin-stimulated gastric secretion, blood glucose and serum electrolyte levels in the unanesthetized rat.

The effect of various doses of serotonin (5-HT) on the basal or insulin-stimulated gastric secretion was studied, for 4 hr after the injection, in unanesthetized rats with chronic gastric fistulas. The blood glucose and serum Na, K and Ca ions concentrations were also determined. Insulin produced hypoglycemia and hypokalemia, most pronounced in the first hr, and increased HCl and pepsin output, with a maximum at 2 hr after the injection. 5-HT significantly inhibited both basal and insulin-stimulated gastric secretion. The amine produced transient hyperglycemia, which was less pronounced in rats simultaneously receiving insulin. The inhibition of insulin-stimulated gastric secretion by 5-HT lasted for a longer period than the prevention of the biochemical changes brought about by insulin. The prevention by 5-HT of insulin hypoglycemia and hypokalemia may be of significant importance in the mechanism of the depression of insulin-stimulated gastric secretion.