Entero-pancreatic reflexes revealed by duodenal anesthesia in the dog

This study was designed to improve our understanding of duodeno-pancreatic reflexes, the existence of which was suggested by the previous observation of a reduction in secretin-stimulated pancreatic secretion during local anesthesia of the duodenal mucosa. The effects on this reduction in secretin-stimulated secretion of cholinergic or adrenergic blocking agents (alone or in combination) and of truncal vagotomy, were studied in conscious dog with gastric and pancreatic fistulae. For each agent and for secretin alone in normal and vagotomized dogs, a comparison was made of pancreatic secretion with and without lignocaine anesthesia of the duodenal mucosa. Lignocaine reduced pancreatic secretion with secretin alone, and stimulated it during infusion of atropine. The changes in both protein bicarbonate secretion were blocked by pentolinium and by phenoxybenzamine whereas propranolol mainly blocked the effects on bicarbonate output. The effect of truncal vagotomy resembled that of atropine. These results suggest the existence of two enteropancreatic reflex mechanisms; an excitory cholinergic vagal reflex and an inhibitory, atropine-resistant non-vagal reflex. Both are blocked by pentolinium (a ganglion blocker) and by phenoxy-benzamine, suggesting the involvement of alpha-adrenergic receptors probably also at the level of the ganglion cell. Beta-adrenergic receptors are also involved in the regulation of bicarbonate and fluid secretion.