Voigt Cornelia, Goymann Wolfgang
Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, D-82319 Seewiesen, Germany.
Dev Neurobiol. 2007 Oct;67(12):1560-73. doi: 10.1002/dneu.20528.
In most bird species males compete over access to females and have elevated circulating androgen levels when they establish and defend a breeding territory or guard a mate. Testosterone is involved in the regulation of territorial aggression and sexual display in males. In few bird species the traditional sex-roles are reversed and females are highly aggressive and compete over access to males. Such species represent excellent models to study the hormonal modulation of aggressive behavior in females. Plasma sex steroid concentrations in sex-role reversed species follow the patterns of birds with "traditional" sex-roles. The neural mechanisms modulating endocrine secretion and hormone-behavior interactions in sex-role reversed birds are currently unknown. We investigated the sex differences in the mRNA expression of androgen receptors, estrogen receptor alpha, and aromatase in two brain nuclei involved in reproductive and aggressive behavior in the black coucal, the nucleus taeniae and the bed nucleus of the stria terminalis. In the bed nucleus there were no sex differences in the receptor or aromatase expression. In the nucleus taeniae, however, we show for the first time, that females have a higher mRNA expression of androgen receptors than males. These results suggest that the expression of agonistic and courtship behavior in females does not depend on elevated blood hormone levels, but may be regulated via increased steroid hormone sensitivity in particular target areas in the brain. Hence, aggression in females and males may indeed be modulated by the same hormones, but regulated at different levels of the neuroendocrine cascade.
在大多数鸟类物种中，雄性为获得与雌性交配的机会而竞争，并且在建立并保卫繁殖领地或守护配偶时，其循环雄激素水平会升高。睾酮参与雄性领地攻击行为和求偶行为的调节。在少数鸟类物种中，传统的性别角色发生了逆转，雌性具有很强的攻击性，并为获得与雄性交配的机会而竞争。这类物种是研究雌性攻击行为的激素调节的极佳模型。性别角色逆转物种的血浆性类固醇浓度遵循具有“传统”性别角色的鸟类的模式。目前尚不清楚在性别角色逆转的鸟类中调节内分泌分泌和激素 - 行为相互作用的神经机制。我们研究了参与黑鸦鹃繁殖和攻击行为的两个脑核——带状核和终纹床核中雄激素受体、雌激素受体α和芳香化酶的mRNA表达的性别差异。在终纹床核中，受体或芳香化酶的表达没有性别差异。然而，在带状核中，我们首次发现雌性的雄激素受体mRNA表达高于雄性。这些结果表明，雌性的攻击行为和求偶行为的表达并不依赖于血液中激素水平的升高，而是可能通过大脑特定靶区域中类固醇激素敏感性的增加来调节。因此，雌性和雄性的攻击行为可能确实由相同的激素调节，但在神经内分泌级联反应的不同水平上进行调控。
