POSSIBLE INVOLVEMENT OF VASOACTIVE INTESTINAL POLYPEPTIDE IN THE CENTRAL STIMULATING ACTION OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE ON PROLACTIN SECRETION IN THE RAT

Effect of pituitary adenylate cyclase-activating polypeptide (PACAP) o n prolactin (PRL) secretion was studied in Wistar strain male rats in vivo. Intravenous injection of PACAP-38 and PACAP-27 resulted in a dos e-related increase in plasma PRL levels both in conscious rats and in urethane-anesthetized rats. In anesthetized animals, i.c.v, injection of PACAP-38 and PACAP-27 also elicited a dose-related increase in plas ma PRL. The PRL secretion induced by i.c.v, injection of PACAP-38 was attenuated by pretreatment with rabbit antiserum to vasoactive intesti nal polypeptide (VIP). These findings suggest that PACAPs stimulate PR L secretion in the rat by acting not only directly on the pituitary bu t also indirectly through the central nervous system, at least partly, via hypothalamic VIP.