Cholinergic mechanisms in the pancreas after extrinsic denervation in the rat

Extrinsic denervations of the pancreas were carried out in rats using bilateral truncal abdominal vagotomy and/or celiac and superior mesenteric ganglionectomy. Chronic fistulas were produced and pancreatic secretion was then measured in conscious animals. In all three groups of extrinsically denervated animals the basal pancreatic secretion was significantly decreased by 15-44% (fluid), 32-59% (bicarbonate output), and 33-43% (protein output). Meal-stimulated secretion was decreased in denervated animals by 38-57% (fluid), 32-44% (bicarbonate output), and 36-64% (protein output). In extrinsically denervated rats, atropine inhibited basal pancreatic fluid by 26-38%, bicarbonate output by 46-71%, and protein output by 63-80%, whereas hexamethonium inhibited basal protein output by 36-58%. These data indicate that cholinergic mechanisms persist in the pancreas after extrinsic denervation. This may correspond either to the spontaneous activity of intrapancreatic excitatory cholinergic neurons or to the drive of these neurons by preganglionic fibers running through nonclassic (such as duodenopancreatic) pathways. No important difference was observed between the effects of vagotomy and those of celiac and superior mesenteric ganglionectomy, indicating that most of the excitatory vagal fibers for the exocrine pancreas run through the celiac pathway and that adrenergic fibers had little effect on the conditions tested.