Abstract
Intravenous injection of serotonin into intact rats caused 2 stages of glycemic response, i. e., initial hypoglycemia followed by marked hyperglycemia. Hyperglycemia was found to be due to the release of epinephrine from adrenal medulla since adrenodemedullated rats showed virtually no hyperglycemic response. Adrenodemedullation as well as anesthesia with sodium pentobarbital sensitized rats to hypoglycemic action of serotonin. Hypoglycemic response was roughly proportional to the dosage, and as low as 50μg per rat resulted in significant hypoglycemia. Subcutaneous and intraperitoneal serotonin showed comparable but less effect. Hypoglycemic effect of serotonin was additive to that of insulin and inhibited epinephrine induced hyperglycemia. Diaphragm of rats injected with serotonin prior to the sacrifice showed increased glucose uptake when incubated in vitro. Glucose as well as inulin tolerance test showed characteristic pattern of concentration curves. Chronically serotonin-treated rats showed increased insulin sensitivity and a little improved glucose tolerance than the control littermates. Possible role of serotonin in carbohydrate metabolism was discussed in conjunction with several reports by other investigators.
