Effect of galanin and vagal integrity on insulin release in dogs

In four conscious dogs infusions of glucose (1 g/kg/h) alone or glucose and galanin (2 micrograms/kg/h) were undertaken during cryogenic vagal blockade at -2 degrees C or following atropine (100 micrograms/kg i.v.). When compared to parenteral glucose alone, the addition of galanin substantially elevated plasma glucose and blunted plasma insulin responses. Vagal blockade or atropine failed to alter these effects of galanin on plasma insulin or glucose responses. Moreover, plasma levels of somatostatin, pancreatic glucagon, pancreatic polypeptide, growth hormone, and cortisol were unaffected by galanin infusions. Thus, the inhibition of plasma insulin responses to glucose by galanin is mediated by a nonvagal, noncholinergic mechanism and is independent of changes in either plasma pancreatic glucagon or somatostatin levels. Galanin at the dose employed in the study may have direct and selective actions on the B cell and thus play an important role in the neuromodulation of insulin release.