Effects of oral finasteride on erectile function in a rat model

Many clinical studies reported finasteride-related erectile dysfunction, but to date, few animal experiments have focused on it.

To investigate the effects of oral finasteride on erectile function in a rat model.

Erectile responses and morphological changes.

Adult, male Sprague-Dawley rats were divided into four groups (25/group): (i) control; (ii) castration; (iii) castration with testosterone (T) replacement; and (iv) oral finasteride treatment. Four weeks later, erectile function was measured by the ratio of intracavernosal pressure and mean arterial blood pressure upon electrical stimulation of the cavernous nerve. Serum T and dihydrotestosterone (DHT) and intraprostatic DHT were measured. The weights and histopathological features of the penile corpus cavernosum and prostate were examined.

Serum T and DHT and intraprostatic DHT concentrations, erectile function, and mean weights of the corpus cavernosum and prostate were lowest in group 2. There was no significant difference in the serum T concentration and erectile function between groups 4 and 1. However, the serum and intraprostatic DHT concentrations were significantly lower in group 4 than in group 1 (both P < 0.001). The tissue weights of the corpus cavernosum and prostate were reduced by 25.9% and 92.3% in group 4 compared with group 1 (both P < 0.001). Histopathology revealed a significant atrophy of the prostate in groups 2 and 4. There was a significant decrease in the smooth muscle content in group 2, but not in groups 3 and 4.

In a rat model, finasteride treatment for 4 weeks reduces the weight of the corpus cavernosum but appears not to affect the erectile responses to electrical stimulation of the cavernous nerve. As erection is a complex process involving important signaling in the brain, further studies are necessary to demonstrate the long-term effects of finasteride on both central and peripheral neural pathways of erection.