Pancreatic vagal nerve is receptive to somatostatin in rats

To investigate whether somatostatin, one of the pancreatic islet hormones, influences the afferent firing activity of the vagus innervating the pancreas and whether there is any relevant morphological basis for the electrophysiological event, cyclic somatostatin-14 was injected into the rat pancreatic artery. The somatostatin injection at a physiological (0.61 pmol) or a pharmacological (3.05 pmol) dose significantly increased the afferent firing discharge rate of the pancreatic vagus in rats anesthetized with urethan and chloralose. The present histological examination disclosed a glomuslike neurovascular body in the rat peripancreatic sinusoidal vein. The body included many small corpuscles, and the corpuscle contained a structure like the afferent nerve ending. The immunohistochemical study revealed that the structure preferentially bound exogenous somatostatin. These electrophysiological and histological findings suggest that the vagal pancreatic nerve is receptive to somatostatin and that there exists a local neural monitoring system for somatostatin secreted from the islets.