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 exoc rine pancreatic secretory functions and their coordination with gastrointes tinal, hepatic, and general homeostatic functions is increasingly recognize d. To better characterize the vagal efferent input to the pancreas, the cap acity of electrical vagal stimulation to induce expression of c-Fos in neur ochemically identified neurons of intrapancreatic ganglia was investigated. At optimal stimulation parameters, unilateral stimulation of either the le ft or right cervical vagus induced Fos expression in similar to 30% of neur ons 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 distal ly cut vagus was applied. Large proportions of neurons contained nitric oxi de synthase as assessed with NADPH diaphorase histochemistry (88%) and chol ine acetyltransferase. The proportion of nitrergic and nonnitrergic neurons receiving vagal input was not different. It is concluded that a significan t proportion of pancreatic neurons receives excitatory synaptic input from vagal preganglionic axons and that many of these vagal postganglionic neuro ns can produce nitric oxide and acetylcholine.