Action of androgen and estrone implants on sexual behavior and reproductive organs of castrated male rabbits

Sexually mature but inexperienced male rabbits were castrated, immediately implanted with either testosterone (T), estrone (E₁), dihydrotestosterone (DHT), T + E₁, or DHT + E₁, and tested for male sexual behavior. Other castrates were not implanted, and testing was either begun immediately (Ca-I) or delayed for 4 weeks (Ca-D). Intact males served as controls (C). Latency to mount a teaser female and to ejaculate into an artificial vagina was tested twice in a morning three times per week for 8 weeks. Then, animals were sacrificed, and reproductive organs were measured. The Ca-I group responded slowly to sexual training and ceased nearly all sexual activity by 8 weeks, whereas the Ca-D males seldom displayed interest in the teaser female. Intact controls and the T and T + E₁, groups all responded to the teaser and mounted and ejaculated within a few seconds. DHT and E₁, individually maintained the sexual activity of castrates equivalent to that of C for 4–5 weeks, but the time required to mount and, particularly, to ejaculate increased thereafter. The results with DHT + E₁ were equivocal in that castrates with this hormone combination sustained sexual activity equivalent to that of the controls for 7 weeks, but one animal in particular became sexually inactive the last week of the experiment. Penis weight was at least partially maintained in all implanted castrates. Accessory sex gland weight was smallest in the DHT group and was significantly increased in the T + E₁ and DHT + E₁ groups. The largest ejaculates of fluid were obtained in the group receiving E₁ alone. These results may be interpreted to indicate a role of both androgen and estrogen centrally and peripherally in the rabbit.