Role of dihydrotestosterone in the control of sexual behaviour on castrated male sheep

Abstract

Wethers (at least 2 1/2 years after castration) were implanted with testosterone propionate (TP), oestradiol dipropionate (ODP), dihydrotestosterone, or a combination of dihydrotestosterone and ODP Silastic capsules. Active immunization against both oestradiol and oestrone or oestradiol only was used to negate effects of oestrogens produced by aromatization of TP. On exposure to oestrous ewes, immunization of wethers implanted with TP significantly (P less than 0.01) reduced all components of mating behaviour (except sniffing and Flehmen) to levels seen in untreated controls. The results support the conclusion that dihydrotestosterone potentiates the action of oestrogens, particularly as regards Flehmen, and has no action on its own within the central nervous system, while oestrogens do not restore mating activity to the same level as that following treatment with testosterone.

Sex Differences in the Distribution and Abundance of Androgen Receptor mRNA‐Containing Cells in the Preoptic Area and Hypothalamus of the Ram and Ewe

“…Part of the actions of testosterone to stimulate reproductive behaviour in rams involves aromatization of testosterone to oestradiol and hence an action via the oestrogen receptor. However, studies involving the use of the nonaromatizable androgen dihydrotestosterone indicate that an additional action at the androgen receptor is necessary for the induction of the full array of reproductive behaviours in rams (23). Chronic treatment with androgens is also able to induce male‐type reproductive behaviour in ovariectomized ewes (3), but acute treatment of ewes with androgens will induce female‐typical reproductive behaviour such as sexual receptivity (4).…”