Effect of cephalic glucose infusion on insulin secretion

The continuous infusion of glucose (1 mg/kg/min) via the carotid artery in anesthetized dogs produces a biphasic pattern of insulin secretion. The first peak reaches a maximum 3 min after glucose infusion and drops to basal level at 7 min. As long as the glucose infusion persists a slow and mantained increase in insulin level in the pancreaticoduodenal vein can be observed. The same amount of glucose infused in the general circulation via the jugular vein provoked a different pattern of insulin secretion. Cerebral glucose infusion to vagotomized dogs also produced a two phase response to insulin secretion, but the levels reached in the first phase were lower that those observed in the normal dogs. The infusion of glucose, via the jugular vein, in vagotomized dogs, failed to induce any change in plasma insulin levels. Our data suggest that a glucose load to the brain induces pancreatic insulin secretion mediated partially by the vagus nerves. These results are also compatible with the hypothesis that a humoral factor could be involved in the pancreatic response.