Cavernosal nerve stimulation in the rat reverses castration-induced decrease in penile NOS activity.

Castration in the rat reduces both the erectile response and penile nitric oxide synthase (NOS) activity, and these effects are prevented by androgen administration. In this study we determined that the decrease of penile NOS in the castrated rat is due to NOS enzyme inhibition rather than to a reduction of its content and that this inhibition may be reversed. Adult rats were either castrated or left intact, and, after 1 wk, electrical field stimulation (EFS) was applied to the cavernosal nerve and the penises were excised either at the peak of erection or after detumescence. Penile NOS activity in the non-EFS castrates decreased by 70% as compared with the intact non-EFS-treated controls, but neuronal NOS content remained unaffected despite changes in regional distribution. NOS activity in the castrated penis was restored to normal values by EFS at the peak of stimulation, and then decreased on detumescence. This was in contrast to the intact controls in which EFS did not stimulate penile NOS activity. These data indicate that androgen depletion in the rat reduces penile NOS activity rather than NOS content and that this enzyme inhibition is reversed by cavernosal nerve stimulation.