Nervous control of pancreatic endocrine secretion in pigs IV. The effect of somatostatin on the insulin and glucagon responses to electrical vagal stimulation and to intraarterial acetylcholine

We studied the effect of a primed i.v. infusion of somatostatin (0.5 μg×min^–1×kg^–1 on the glucose dependent insulin and glucagon responses to electrical stimulation of the vagus nerves or to i.a. acetylcholine in anesthetized pigs. Somatostatin completely abolished the insulin and glucagon responses to ongoing vagal stimulation; after 70 min somatostatin infusion the response to reiterated stimulation was profoundly inhibited. After termination of the somatostatin infusion, a considerable rebound secretion of insulin and glucagon was noted. By contrast, the endocrine response to acetylcholine persisted in spite of the somatostatin administration. Blood glucose increased slightly during somatostatin infusion. The results suggest that somatostatin inhibits the responses to vagal stimulation by interference with the neural transmission to the pancreatic islets rather than by inhibition of the islet cells themselves; acetylcholine may be involved in this neural transmission (acting on nicotinic receptors.