CENTRAL ADMINISTRATION OF PACAP STIMULATES GASTRIC-SECRETION MEDIATEDTHROUGH THE VAGAL PATHWAY IN ANESTHETIZED RATS

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neurop eptide that was originally isolated from ovine hypothalamic tissue. Th e peptide has two amidated forms, PACAP38 and PACAP27. In this study, we examined the effects of centrally administered PACAP38 and PACAP27 on gastric secretion in anesthetized rats. Centrally administered PACA P stimulated gastric acid and pepsin secretion in a dose-dependent man ner. PACAP38 was 1.5-2 times more potent than PACAP27 on gastric secre tion. By contrast, intravenously administered PACAP38 had no effect on basal or pentagastrin-stimulated gastric secretion. PACAP6-38, a PACA P antagonist, by itself at high doses also stimulated gastric and peps in secretion, but at lower doses had no effect. Centrally administered PACAP6-38 at a dose that had no effect on gastric secretion, atropine pretreatment, or vagotomy pre;treatment, suppressed the stimulatory e ffect of PACAP38. It is concluded that centrally administered PACAP ma y have a regulatory effect on gastric secretion through PACAP receptor s and the vagal pathway.