PANCREATIC-POLYPEPTIDE STIMULATES GASTRIC-ACID SECRETION THROUGH A VAGAL MECHANISM IN RATS

The present study examined the effect of pancreatic polypeptide (PP) o n gastric acid secretion. A 45-min infusion of PP was delivered into t he jugular vein of urethan-anesthetized rats. Rat PP (100 pmol) signif icantly increased acid secretion over baseline; bilateral cervical vag otomy or peripheral atropine both eliminated this acid response. Neith er intraperitoneal infusion nor close intra-arterial infusion of 100 p mol PP into the gastric circulation altered acid secretion. These resu lts suggest that although PP requires intact vagal reflexes to stimula te acid output, it does not act on afferent or presynaptic efferent te rminals of the vagus or directly within the stomach. Given that vagal reflexes consist of an afferent limb, an efferent limb, and a central relay, it may be that the target of circulating PP lies within the cen tral nervous system. Indeed, previous studies from our laboratory have shown that microinjection of PP into the dorsal vagal complex results in long-lasting vagal-dependent elevation of gastric acid secretion.