In the present study, we evaluated the effects of central administration of pancreatic polypeptide (PP) on gastric emptying of a liquid meal in conscious rats using a phenol red method. Intracisternal injection of PP (0.5-2.0 micrograms) speeds gastric emptying of a test meal in a dose-dependent manner. In contrast, i.p. injection of PP at the same doses inhibited gastric emptying in a dose-related fashion. Bilateral gastric branch vagotomy abolished the increase in gastric emptying evoked by intracisternal PP. These results demonstrate that PP speeds gastric emptying through the vagal system when given centrally but slows emptying when given peripherally.