Soma K K, Bindra R K, Gee J, Wingfield J C, Schlinger B A
Department of Zoology, University of Washington, Box 351800, Seattle, Washington 98195-1800, USA.
J Neurobiol. 1999 Nov 5;41(2):176-88.
The Lapland longspur (Calcarius lapponicus) is an arctic-breeding songbird that shows rapid behavioral changes during a short breeding season. Changes in plasma testosterone (T) in the spring are correlated with singing but not territorial aggression in males. Also, T treatment increases song but not aggression in this species. In contrast, in temperate-zone breeders, song and aggression are highly correlated, and both increase after T treatment. We asked whether regional or temporal differences in androgen-metabolizing enzymes in the longspur brain explain hormone-behavior patterns in this species. We measured the activities of aromatase, 5alpha-reductase and 5beta-reductase in free-living longspur males. Aromatase and 5alpha-reductase convert T into the active steroids 17beta-estradiol (E(2)) and 5alpha-dihydrotestosterone (5alpha-DHT), respectively. 5beta-Reductase deactivates T via conversion to 5beta-DHT, an inactive steroid. We examined seven brain regions at three stages in the breeding season. Overall, aromatase activity was high in the hypothalamus, hippocampus, and ventromedial telencephalon (containing nucleus taeniae, the avian homologue to the amygdala). 5beta-Reductase activity was high throughout the telencephalon. Activities of all three enzymes changed over time in a region-specific manner. In particular, aromatase activity in the rostral hypothalamus was decreased late in the breeding season, which may explain why T treatment at this time does not increase aggression. Changes in 5beta-reductase do not explain the effects of plasma T on aggressive behavior.
拉普兰铁爪鹀（Calcarius lapponicus）是一种在北极繁殖的鸣禽，在短暂的繁殖季节会表现出快速的行为变化。春季雄性血浆睾酮（T）的变化与鸣叫相关，但与领地攻击性无关。此外，T处理会增加该物种的鸣叫，但不会增加攻击性。相比之下，在温带繁殖的鸟类中，鸣叫和攻击性高度相关，且在T处理后两者都会增加。我们研究了铁爪鹀大脑中雄激素代谢酶的区域或时间差异是否能解释该物种的激素 - 行为模式。我们测量了自由生活的雄性铁爪鹀体内芳香化酶、5α - 还原酶和5β - 还原酶的活性。芳香化酶和5α - 还原酶分别将T转化为活性类固醇17β - 雌二醇（E₂）和5α - 双氢睾酮（5α - DHT）。5β - 还原酶通过将T转化为无活性的类固醇5β - DHT使T失活。我们在繁殖季节的三个阶段检查了七个脑区。总体而言，下丘脑、海马体和腹内侧端脑（包含带状核，鸟类杏仁核的同源物）中的芳香化酶活性较高。整个端脑的5β - 还原酶活性都很高。所有三种酶的活性都以区域特异性的方式随时间变化。特别是，繁殖季节后期喙端下丘脑的芳香化酶活性降低，这可能解释了此时T处理为何不会增加攻击性。5β - 还原酶的变化并不能解释血浆T对攻击行为的影响。
