Regulation of LH Secretion in a Seasonally Breeding Bird

大多数动物的繁殖发生在一年中饲养幼崽的最佳季节。这项研究通过调节生殖必需激素黄体生成素(ı)的分泌机制，探索了美洲树雀季节性繁殖的生理控制。以前的工作已经确定，当雄性麻雀从每天的短光周期转移到较长的光周期(例如，从8小时)时，黄体生成素的分泌增加。每天到20小时的光照。每天的光照)。有两种机制控制黄体生成素的分泌：一种类似于节流阀，驱动黄体生成素的分泌；另一种类似于刹车，抑制黄体生成素的分泌。每天长时间的光周期具有刺激性，因为它增加了对黄体生成素分泌的驱动，而不是刹车，并在很大程度上决定了长期暴露在每天长时间光周期下的鸟类繁殖季节的开始和结束。减少对激素分泌的驱动或调节刹车以终止或控制从非繁殖状态到繁殖状态的转变的机制分别尚不清楚。这项调查特别探讨(A)暴露在每日短光周期下的雄性树雀对黄体生成素分泌的驱动是否与日长有关；(B)眼睛是否是在繁殖季节结束时减少对黄体生成素分泌的驱动并调节对黄体生成素分泌的刹车的机制的组成部分；以及(C)恢复对黄体生成素分泌的驱动与加强刹车之间的关系。研究结果将阐明季节性繁殖开始和终止的一般生理原理，并为季节性繁殖的家养和/或野生(包括猎物和害虫)物种提出改进的管理策略。

Reproduction in most species of animals occurs during that season of the year when conditions for raising young are optimal. This study explores physiological control of seasonal reproduction in the American tree sparrow by focusing on the mechanisms that regulate secretion of an essential hormone of reproduction ıluteinizing hormone) (LH)!. Previous work has established that LH secretion increases when male tree sparrows are transferred from a short to a long daily photoperiod (for example, from 8 hr. of light per day to 20 hrs. of light per day). Two mechanisms control LH secretion: one is analogous to a throttle and drives LH secretion; the other is analogous to a brake and retards LH secretion. A long daily photoperiod is stimulatory because it augments the drive on LH secretion, rather than in the brake, and largely determines when the reproductive season begins and ends in birds exposed chronically to long daily photoperiods. The mechanisms that decrease the drive on hormone secretion or modulate the brake to terminate or control the transition from the non-breeding to the breeding state, respectively, are not understood. This investigation specifically explores (a) whether the drive on LH secretion in male tree sparrows exposed to short daily photoperiods is daylength-dependent; (b) whether the eyes are components of the mechanism that decreases the drive on LH secretion at the end of the breeding season and modulates the brake on LH secretion; and (c) the relationship between restoring the drive on LH secretion and intensifying the brake. The results will clarify general physiological principles underlying initiation and termination of seasonal reproduction and suggest improved management strategies for domestic and /or wild (including game and pest) species that breed seasonally.