Peripheral and central androgenic stimulation of sexual behaviour of castrated male rats

The effects of androgens on the maintenance and restoration of sexual behaviour (mounts, intromissions and ejaculations) of castrated male rats were studied. In the maintenance study the rats were treated during 5 weeks, starting one day following castration. Testosterone propionate maintained sexual behaviour at an almost normal level. The androgenoestrogen intermediate 19-hydroxytestosterone propionate was unable to prevent the decline in the number of ejaculations over the weeks although this hormone maintained the post-ejaculatory refractory period in those rats that ejaculated and also maintained normal sexual latencies. In the restoration study administration of testosterone propionate during 7 weeks to long-term castrated rats restored sexual behaviour to normal. 19-Hydroxytestosterone propionate treated rats displayed mounts but no other signs of sexual behaviour. The 5alpha-reduced androgen dihydrotestosterone propionate did not restore sexual behaviour. Testosterone propionate and dihydrotestosterone propionate stimulated peripheral target organs; 19-hydroxytestosterone propionate was ineffective in this respect. It has been suggested that testosterone might stimulate sexual behaviour in rats in two ways, i.e., via its aromatization to oestradiol in the brain, andy by stimulating growth of peripheral tissues via its 5alpha-reduction to dihydrotestosterone. In support for this view we have found that the combination of 19-hydroxytestosterone propionate and dihydrotestosterone propionate was effective in restoring the full pattern of sexual behaviour in castrated male rats.