Aromatizable and 5alpha-reduced androgens: differentiation between central and peripheral effects on male rat sexual behavior.

Sexual behavior was observed in the 5 wk after castration in four separate experiments. In each, 50 male rats were allocated equally to the following treatment groups; intact controls; castrated controls; castrated + testosterone propionate, 75 μg/day; castrated + test steroid 1, 150 μg/day; castrated + test steroid 2, 150 μg/day. The following propionated compounds were used; dihydrotestosterone, androsterone, 3α- and 3β-androstanediols, androstenedione, androstanedione, 19-hydroxyandrostenedione, estradiol. With the exception of androstanedione, only aromatizable androgens or estrogen prevented post-castration increases in refractory period durations. However, aromatizable and 5α-reduced androgens stimulated penile spine growth. In each experiment there was a significant positive correlation between spine number and copulatory efficiency i.e., the ratio of intromission to mount frequencies.