Location and Neuroendocrine Function of Putative Encephalic Photoreceptors

摘要许多脊椎动物，包括各种鸟类，每年都预测季节变化，用于预测季节发生的环境线索是日长或光周期。 多年来，科学家们一直假设鸟类具有感光器和神经系统，这些系统旨在记录白天的长度和这些信息，以确定迁徙或繁殖和成功养育后代的适当时间。 一个仍然没有答案的问题是，用于季节信息的光感受器位于哪里，它们是如何工作的？ 光感受器已经定位在眼睛、松果体和大脑中。 科学家将大脑中的光感受器称为脑光感受器（EPR）。 几种鸟类所表现出的最强有力的季节性事件之一是，当日照长度增加时，生殖系统迅速发育。 因此，重要的是要评估可能在这种现象中发挥作用的每一组受体。 将利用快速刺激性腺发育的技术与针对已知存在光感受器的解剖部位的显微外科技术相结合，以确定哪组受体在生殖系统的季节性生长中发挥作用，例如性腺的发育。 在本研究中，将利用细胞培养程序来保持光感受器存活数小时，以确定细胞是否响应于直接闪光而显著降低钙浓度。 这些实验应该（1）确定EPR是否是小鸡生殖系统发育的唯一原因，（2）为本科生和研究生提供积极的研究经验。 这些结果为遗传学家负责监测国内或野生种鸡群提供了重要信息。 鸟类遗传学家可以选择性地选择繁殖鸡群，表现出增加的数量或反应的EPR光，以最大限度地提高反应的成熟小鸡光周期操纵，从而提高繁殖效率。

Lay Abstract Many vertebrates, including various species of birds anticipate seasonal changes each year and an environmental cue utilized to predict the occurrence of seasons is day length or photoperiod. For many years scientists have hypothesized that avian species have photoreceptors and neural systems designed to register day length and this information to determine the opportune time to migrate or to reproduce and raise young successfully. A question that remains unanswered is, where are the photoreceptors utilized for seasonal information located and how do they work? Photoreceptors have been localized in the eyes, pineal gland, and brain. Scientists refer to photoreceptors in the brain as encephalic photoreceptors (EPRs). One of the most robust, seasonal events displayed by several avian species is rapid development of the reproductive system when day length has increased. Therefore it is important to evaluate each set of receptors that could play a role in this phenomenon. A combination of techniques that rapidly stimulate development of the gonads coupled with microsurgical techniques directed to anatomical sites where photoreceptors are known to occur, will be utilized to determine which group of receptors play a role in seasonal growth of the reproductive system, such as development of the gonads. In the present studies a cell culture procedure will be utilized to keep photoreceptors viable for hours, to determine whether cells respond to direct flashes of light with a significant reduction in calcium concentration. These experiments should (1) establish whether or not EPRs are solely responsible for development of the reproductive system in chicks, and (2) positive research experience to both undergraduate and graduate students.. These results provide important information for geneticists responsible for monitoring domestic or wild breeder flocks. Avian geneticists could selectively choose breeder flocks that exhibit increased numbers or responses of EPRs to light to maximize the response of maturing chicks to photoperiodic manipulation thereby increasing reproductive efficiency.