[Distribution of NADPH diaphorase-positive nerves in human penile tissue]

Recently, nitric oxide (NO) has been thought to be a neuronal messenger to evoke penile erection. NO synthase (NOS)-containing nerve fibers were identified and localized in human penile tissue, but detail distribution of NOS-containing nerve fibers in the human penis was unclear. In the present study we examined their distribution using histochemical staining of NADPH diaphorase (ND), which is a specific marker of neuronal NOS. In the crura penis some various sizes of ND-positive nerve bundles were observed in the cavernous spaces. In the penile shaft large bundles (> 50 microns) decreased in number and were observed only near deep artery. There were abundant ND-positive nerve terminals with fine varicosity innervating both corpus cavernous smooth muscles and deep, dorsal and helicine arteries. In the wall of deep dorsal vein there were also many groups of ND-positive fibers. Endothelium of deep artery and its large branches was clearly ND-positive, but parts of endothelium of deep dorsal vein or corpus cavernous sinus were only faintly stained. Some of the dorsal penile nerve fibers were ND-positive. In corpus spongiosum many ND-positive nerve fibers were observed and urethelium was clearly ND-positive. In conclusion, NO may have an important role in the function of both corpus cavernosum and corpus spongiosum because NOS-containing nerve fibers were widely distributed in both cavernous tissues.