Neural control of islet function by norepinephrine and sympathetic neuropeptides.

It is clear that the sympathoadrenal system has a role in the regulation of endocrine pancreatic function and that the sympathetic nerves of the pancreas can change pancreatic hormone secretion to increase the availability of metabolic fuels. It seems likely that the classical sympathetic neurotransmitter, NE, acts in concert with peptide co-transmitters, such as galanin and NPY. Each is released during the stimulation of pancreatic sympathetic nerves and each is capable of influencing either islet function or pancreatic blood flow. There is considerable indirect evidence that the sympathetic innervation of the pancreas is activated during acute stress and influences the endocrine pancreas. However, proving such a physiologic role is difficult because of redundant mechanisms that influence the secretion of the metabolically-crucial hormones, insulin and glucagon. Such definitive proof therefore awaits the development of new techniques to dissect and dissociate these mechanisms.