Soma K K, Sullivan K A, Tramontin A D, Saldanha C J, Schlinger B A, Wingfield J C
Department of Zoology, University of Washington, Seattle 98195, USA.
J Comp Physiol A. 2000 Jul-Aug;186(7-8):759-69. doi: 10.1007/s003590000129.
Many studies have demonstrated that male aggression is regulated by testosterone. The conversion of testosterone to estradiol by brain aromatase is also known to regulate male aggression in the breeding season. Male song sparrows (Melospiza melodia morphna) are territorial not only in the breeding season, but also in the nonbreeding season, when plasma testosterone and estradiol levels are basal. Castration has no effect on nonbreeding aggression. In contrast, chronic (10 day) aromatase inhibitor (fadrozole) treatment decreases nonbreeding aggression, indicating a role for estrogens. Here, we show that acute (1 day) fadrozole treatment decreases nonbreeding territoriality, suggesting relatively rapid estrogen effects. In spring, fadrozole decreases brain aromatase activity, but acute and chronic fadrozole treatments do not significantly decrease aggression, although trends for some behaviors approach significance. In gonadally intact birds, fadrozole may be less effective at reducing aggression in the spring. This might occur because fadrozole causes a large increase in plasma testosterone in intact breeding males. Alternatively, estradiol may be more important for territoriality in winter than spring. We hypothesize that sex steroids regulate male aggression in spring and winter, but the endocrine mechanisms vary seasonally.
许多研究表明，雄性的攻击性受睾酮调节。大脑芳香化酶将睾酮转化为雌二醇也被认为在繁殖季节调节雄性的攻击性。雄性歌带鹀（Melospiza melodia morphna）不仅在繁殖季节具有领地意识，在非繁殖季节也如此，此时血浆睾酮和雌二醇水平处于基础状态。阉割对非繁殖期的攻击性没有影响。相反，长期（10天）使用芳香化酶抑制剂（法倔唑）治疗可降低非繁殖期的攻击性，表明雌激素发挥了作用。在此，我们表明急性（1天）法倔唑治疗可降低非繁殖期的领地行为，提示雌激素作用相对迅速。在春季，法倔唑会降低大脑芳香化酶活性，但急性和长期法倔唑治疗均未显著降低攻击性，尽管某些行为的变化趋势接近显著水平。在性腺完整的鸟类中，法倔唑在春季降低攻击性的效果可能较差。这可能是因为法倔唑会使处于繁殖期性腺完整的雄性血浆睾酮大幅增加。或者，雌二醇对冬季领地行为的重要性可能高于春季。我们推测，性类固醇在春季和冬季调节雄性的攻击性，但内分泌机制随季节变化。
