Importance of cholinergic innervation of the pancreas for glucose tolerance in the rat.

Because cholinergic innervation of the pancreas is of importance in control of oral glucose tolerance, it seems important to determine whether transplanted pancreatic tissue becomes reinnervated with cholinergic fibers. Oral and intravenous glucose tolerance tests (ivGTT) were performed with and without atropine treatment on streptozotocin-diabetic rats treated by intraportal transplantation of isogenic islets 13-15 wk previously and on sham-operated nondiabetic controls. Atropine had no effect on the ivGTT of transplanted rats or controls. In controls atropine caused a deterioration of the oral glucose tolerance, abolished the preabsorptive insulin release, and also diminished the early part of the glucose-induced insulin release in these animals. In the absence of atropine, transplanted rats had pathological oral glucose tolerance, preabsorptive insulin release was absent, and glucose-induced insulin release was diminished compared to controls. Atropine had little effect on the oral GTT of transplanted rats. The present results underline the importance of the vagus nerve in the control of oral glucose tolerance and show that the vagus nerve in rats, at least under these experimental conditions, does not modulate the insulin response to intravenous glucose. The results suggest that intraportally transplanted islets remain functionally vagotomized.