Functional vagal input to chemically identified neurons in pancreatic ganglia as revealed by Fos expression.

The importance of neural elements in the control of both endocrine and exocrine pancreatic secretory functions and their coordination with gastrointestinal, hepatic, and general homeostatic functions is increasingly recognized. To better characterize the vagal efferent input to the pancreas, the capacity of electrical vagal stimulation to induce expression of c-Fos in neurochemically identified neurons of intrapancreatic ganglia was investigated. At optimal stimulation parameters, unilateral stimulation of either the left or right cervical vagus induced Fos expression in approximately 30% of neurons in the head and 10-20% of neurons in the body and tail of the pancreas. There was no Fos expression if no stimulation or stimulation with a distally cut vagus was applied. Large proportions of neurons contained nitric oxide synthase as assessed with NADPH diaphorase histochemistry (88%) and choline acetyltransferase. The proportion of nitrergic and nonnitrergic neurons receiving vagal input was not different. It is concluded that a significant proportion of pancreatic neurons receives excitatory synaptic input from vagal preganglionic axons and that many of these vagal postganglionic neurons can produce nitric oxide and acetylcholine.