Hormonal control of female sexual behavior in the Japanese quail

Four experiments were carried out to study the hormonal control of female receptivity and proceptivity in Japanese quail. Both aspects of reproductive behavior can be activated in a dose-dependent manner by injections of estradiol benzoate (EB). Progesterone (P) given in addition to suboptimal doses of EB has little additional stimulatory effect. Other aspects of the reproductive physiology such as enlargement of the cloacal diameter and growth of the oviduct also seem to be controlled primarily by estrogens with little or no additive effect of P. These conclusions were confirmed by injecting egg-laying females with an antiestrogen, tamoxifen, or an antiprogestin, RU38486. Only the former had marked effects on sexual receptivity, cloacal diameter, and oviduct weight. The inhibiting effects of tamoxifen could easily be reversed by injecting females with large doses of estrogen, which demonstrates that tamoxifen acts on an estrogen-dependent mechanism and not through nonspecific effects.