Estrogens play a key role in the sexual differentiation of the brain and behavior. While early estrogen actions exert masculinizing effects on the brain of male rodents, a diametrically opposite effect is observed in birds where estrogens demasculinize the brain of females. Yet, the two vertebrate classes express similar sex differences in the brain and behavior. Although ERα is thought to play a major role in these processes in rodents, the role of ERβ is still controversial. In birds, the identity of the estrogen receptor(s) underlying the demasculinization of the female brain remains unclear. The aim of the present study was thus to determine in Japanese quail the effects of specific agonists of ERα (propylpyrazole triol, PPT) and ERβ (diarylpropionitrile, DPN) administered at the beginning of the sensitive period (embryonic day 7, E7) on the sexual differentiation of male sexual behavior and on the density of vasotocin-immunoreactive (VT-ir) fibers, a known marker of the organizational action of estrogens on the quail brain. We demonstrate that estradiol benzoate and the ERβ agonist (DPN) demasculinize male sexual behavior and decrease the density of VT-ir fibers in the medial preoptic nucleus and the bed nucleus of the stria terminalis, while PPT has no effect on these measures. These results clearly indicate that ERβ, but not ERα, is involved in the estrogen-induced sexual differentiation of brain and sexual behavior in quail.

雌激素在大脑和行为的性别分化中起着关键作用。虽然早期的雌激素作用对雄性啮齿动物的大脑产生男性化作用，但在鸟类中观察到截然相反的作用，雌激素使雌性的大脑去男性化。然而，这两种脊椎动物在大脑和行为上表现出相似的性别差异。尽管 ERα 被认为在啮齿动物的这些过程中起主要作用，但 ERβ 的作用仍然存在争议。在鸟类中，雌性大脑去男性化背后的雌激素受体的身份仍不清楚。因此，本研究的目的是在日本鹌鹑中确定在敏感期开始时（胚胎第 7 天，E7) 关于男性性行为的性别分化和血管收缩素免疫反应 (VT-ir) 纤维的密度，这是雌激素对鹌鹑大脑的组织作用的已知标志物。我们证明雌二醇苯甲酸酯和 ERβ 激动剂 (DPN) 使男性性行为去男性化并降低内侧视前核和终纹床核中 VT-ir 纤维的密度，而 PPT 对这些措施没有影响。这些结果清楚地表明 ERβ 而不是 ERα 参与雌激素诱导的大脑性分化和鹌鹑的性行为。我们证明雌二醇苯甲酸酯和 ERβ 激动剂 (DPN) 使男性性行为去男性化并降低内侧视前核和终纹床核中 VT-ir 纤维的密度，而 PPT 对这些措施没有影响。这些结果清楚地表明 ERβ 而不是 ERα 参与雌激素诱导的大脑性分化和鹌鹑的性行为。我们证明雌二醇苯甲酸酯和 ERβ 激动剂 (DPN) 使男性性行为去男性化并降低内侧视前核和终纹床核中 VT-ir 纤维的密度，而 PPT 对这些措施没有影响。这些结果清楚地表明 ERβ 而不是 ERα 参与雌激素诱导的大脑性分化和鹌鹑的性行为。