Selective pancreatic nerve section. An investigation of neural control of glucagon release in the conscious unrestrained dog

Plasma glucagon, insulin and glucose concentrations were determined in conscious, unrestrained dogs that had fasted overnight, before, and again at 3 weeks and 4 months after section of the nerve bundles that pass along the cranial pancreatico-duodenal artery to the pancreas. 1. Section of these nerves caused a persistent decrease of the plasma glucagon concentration by about 60% of the preoperative value. In contrast, plasma insulin concentration was unaffected. 2. Plasma glucose level was unaltered 3-4 weeks after denervation, but was significantly decreased (by about 20%) 3-4 months after the operation. 3. Before denervation, moderate exercise caused a gradual rise in plasma glucagon concentration, together with a slight decrease in plasma glucose concentration without any detectable change in plasma insulin concentration. After denervation, the increase in plasma glucagon concentration was abolished and a gradual decrease in plasma insulin concentration, together with a slight rise in plasma glucose concentration were observed. 4. It is concluded that more than half the glucagon that is released from the pancreas in the normoglycaemic, conscious, unrestrained dog can be attributed to the tonic activity of the autonomic nervous system which, under he same experimental conditions, was found to have a negligible effect on insulin secretion.