Histochemical demonstration of NADPH-diaphorase activity, a marker for nitric oxide synthase, in neurons of the rat pancreas

To clarify the role of nitric oxide (NO) in the pancreas, we histochemically investigated NADPH-diaphorase, a marker for NO synthase, in the rat pancreas. NADPH-diaphorase activity was localized in the neurons and endothelium of vessels. The nerve fibers with NADPH-diaphorase activity were observed in both the exocrine and the endocrine pancreas associated chiefly with the vascular systems. Most nerve cell bodies (98.5%) within the pancreatic parenchyma showed strong activity for this enzyme. These results suggest that NO may participate in the hemodynamic control of the pancreas and in the neuronal regulation of pancreatic exocrine and endocrine functions.