Control of Seasonal Breeding in American Tree Sparrows

美洲树雀的睾丸生长发生在春季，以响应日长的增加。到初夏，雄性树雀对漫长的白天变得反应迟钝(也就是说，它们变得不能照相)，它们的睾丸退化。这个项目探索了开启和关闭季节性繁殖的生理机制。第一阶段测试的假设是：(1)一种甲状腺激素(T4)模拟长白天(和甲状腺切除，短白天)，以及(2)为了诱导光折射，当雄性树雀经历长白天时，T4必须可用。第二阶段研究大脑兴奋性氨基酸受体(例如，L-谷氨酸)将光信息(来自大脑光感受器、生物钟和/或其他地方)传递到控制脑下垂体生殖激素分泌的神经元的假说。该项目的最终目标是加强和扩大对季节性繁殖的生理基础的了解。

Testicular growth in American tree sparrows occurs in spring in response to increasing daylength. By early summer, male tree sparrows become unresponsive to long days (i.e., they become photorefractory), and their testes regress. This project explores the physiological mechanisms that turn seasonal breeding on and off. The first phase tests the hypotheses that (1) a thyroid hormone (T4) simulates longs days (and thyroidectomy, short days), and (2) for photorefractoriness to be induced, T4 must be available when male tree sparrows experience long days. The second phase examines the hypothesis that brain receptors for excitatory amino acids (e.g., L-glutamate) transmit processes photic information (from brain photoreceptors, the biological clock, and/or elsewhere) to neurons that control the secretion of reproductive hormones from the pituitary gland. The ultimate goal of the project is to strengthen and extend understanding of the physiological basis of seasonal reproduction.//