Cerebral insulin can regulate glucose homeostasis via activation of the parasympathetic nervous system, which results in the reduction of hepatic glucose output. However, the precise mechanism (s) through which cerebral insulin directly exerts an effect on insulin secretion remains unclear. In the present study, we found that cerebral administration of insulin caused an increase of plasma insulin concentration and a concomitant decrease in plasma glucose levels within one hour. These effects were blocked by vagotomy or intraperitoneal injection of 1, 1-dimethyl-4-diphenylacetoxypiperidinium iodide, a specific M 3 antagonist. The mediating influence of parasympathetic activation can thus be considered. The adenosine triphosphate-sensitive potassium (K-ATP) channel is a key mediator of the cerebral action of insulin. The plasma glucose-lowering action of insulin was abolished by cerebral administration of glibenclamide or repaglinide at concentrations sufficient to block K-ATP channels. In conclusion, our findings suggest that cerebral insulin may induce insulin release by stimulating the opening of K-ATP channels, which in turn activate parasympathetic tone in pancreatic tissue.