Postnatal development of penile NADPH diaphorase in male rats (Rattus norvegicus): an indicator of erectile function

The aim of this study was to determine the contribution of nitric oxide (NO) to the development of penile erection in rats and was accomplished by evaluating the nicotinamide adenine dinucleotide phosphate diaphorase (NADPH) content of juvenile penile tissues. NADPH is an enzyme involved in the synthesis of NO, a mediator of smooth muscle relaxation in penile tissues. We euthanized 36 rats (age, 1 to 65 days) and obtained penile midshaft specimens for NADPH staining. The number of NADPH-positive granules in the corpus cavernosum and dorsal penile nerve increased significantly (P < 0.001) until animals were 50 days of age. Penile erections in young rats are known to occur around 30-40 days, and penile tissues showed a very significant (P < 0.001) increase of NADPH-positive granules in the corpus cavernosum and the dorsal penile nerve during this period. Therefore, NO seems important for the development of penile erection in juvenile rats.