Somatostatin inhibits neurally stimulated pancreatic secretion indirectly

We studied the effect of a primed i.v. infusion of somatostatin (100 micrograms as a bolus, 0.5 micrograms x kg-1 x min-1) on pancreatic exocrine secretion in response to electrical stimulation of the vagus nerves and intra-arterial infusions of acetylcholine (0.5 mg x min-1) in anesthetized pigs (17-22 kg). In control experiments, vagus stimulation and acetylcholine increased protein secretion 31- to 80-fold and 106-fold, respectively. Somatostatin inhibited the response to vagus stimulation by more than 90%, whereas the response to acetylcholine remained unaffected. It is concluded that the inhibitory action of somatostatin on the vagally induced secretion must be due to an inhibition of the impulse transmission in the efferent parasympathetic nerves to the pancreas, and it is suggested that this mechanism contributes to the inhibitory effect of somatostatin observed with other stimuli as well.