EFFECTS OF INTRAVENOUSLY INFUSED PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE ON ARGININE-VASOPRESSIN AND OXYTOCIN SECRETION IN MAN

IN ORDER to establish possible stimulatory effects of increasing plasma concentrations of pituitary adenylate cyclase-activating polypeptide (PACAP) on arginine vasopressin (AVP) and/or oxytocin (OT) secretion, successively increasing doses of PACAP-38 (2, 4 and 8 pmol kg min(-1); each dose for 20 min) were infused in seven normal men. Plasma AVP and OT levels were measured before infusion and every 20 min, just before increasing the infusion dose of PACAP. During tests, PACAP infusion did not produce untoward side effects or changes in blood osmolality and/or pressure. Plasma OT levels did not change during PACAP infusion. Plasma AVP concentrations were not modified by infusion of the lowest-dose of PACAP, whereas they were significantly increased in a dose-response fashion when higher amounts of PACAP were given. These findings demonstrate for the first time in humans that the systemic administration of PACAP exerts stimulatory effects on AVP, but not OT secretion.