Pancreatic polypeptide response to a meal before and after cutting the extrinsic nerves of the upper gastrointestinal tract and the pancreas in the dog

The role of the sympathetic and parasympathetic innervation in the release of pancreatic polypeptide (PP) basally and in response to a meal was studied after stepwise extrinsic denervation of the pancreas and the upper gastrointestinal tract in conscious dogs with gastric fistulae. One set of seven dogs was fed a meat meal (35 g/kg body weight) before and after truncal vagotomy and after truncal vagotomy plus celiac and superior mesenteric ganglionectomy, ie, extrinsic denervation of the pancreas and the upper gastrointestinal tract. In another set of six dogs, only ganglionectomy was performed. Experiments were repeated in the presence of atropine (50 g/kg body weight, given as an intravenous bolus 60 min prior to the meal). Truncal vagotomy significantly (P<0.05) reduced the postprandial 120-min integrated plasma PP response (IPPPR) by 84% as compared to the prevagotomy response. Before truncal vagotomy, atropine significantly reduced the IPPPR by 57%. After truncal vagotomy, atropine completely abolished the residual PP response. Additional celiac and superior mesenteric ganglionectomy did not alter the IPPPR already reduced by truncal vagotomy. With the vagus nerves intact, ganglionectomy alone had no effect on the IPPPR whether or not atropine was given. These findings indicate that (1) the splanchnic nerves do not play a significant role in postprandial PP release and (2) that the vagus nerves are important mediators of the response to a meal. The effect of atropine on postprandial PP release after truncal vagotomy may be due to interruption of short enteropancreatic reflexes, suppression of the intrinsic cholinergic activity of the pancreas, or inhibition of hormonally induced PP release.