Materials and Methods: Animal and human studies pertaining to nitric oxide in the penis were reviewed and analyzed in the context of current descriptions of the molecular biology and physiological effects of this chemical.

Results: Potential sources of nitric oxide in the penis include neurons, sinusoidal endothelium and corporeal smooth muscle cells. Nitric oxide is perceived to exert a host of functional roles by binding with specific molecular targets. Its synthesis and action in the penis are influenced by many different regulatory factors.

Conclusions: Nitric oxide exerts a significant role in the physiology of the penis, operating chiefly as the principal mediator of erectile function. Alterations in the biology of nitric oxide likely account for various forms of erectile dysfunction. The diverse physiological roles of nitric oxide suggest that it may also directly contribute to or cause pathological consequences involving the penis.