NEURAL AND ENDOTHELIAL NITRIC-OXIDE SYNTHASE ACTIVITY IN RAT PENILE ERECTILE TISSUE

NADPH-diaphorase (NADPH-D) activity and immunoreactivity for neural an d endothelial nitric oxide synthase (nNOS and eNOS, respectively) were used to investigate nitric oxide (NO) regulation of penile vasculatur e. Both the histochemical and immunohistochemical techniques for NOS s howed that all smooth muscles regions of the penis (dorsal penile arte ry and vein, deep penile vessels, and cavernosal muscles) were richly innervated. The endothelium of penile arteries, deep dorsal penile vei n, and select veins in the crura and shaft were also stained for NADPH -D and eNOS. However, the endothelium of cavernous sinuses was unstain ed by both techniques. Fewer fibers were seen in the glans penis, thos e present being associated with small blood vessels and large nerve bu ndles near the trabecular walls. All penile neurons in the pelvic plex us, located by retrograde transport of a dye placed in the corpora cav ernosa penis, were stained by the NADPH-D method. Essentially similar results were obtained with an antibody to nNOS. These data suggest tha t penile parasympathetic neurons comprise a uniform population, as all seem capable of forming nitric oxide. However, in contrast to the end othelium of penile vessels, the endothelium lining the cavernosal spac es may not be capable of nitric oxide synthesis.