Identification of Encephalic Photoreceptors

9315307设备已经确定，各种各样的生物都有内部生物钟，这些生物钟有助于使它们与环境变化的每日（即昼夜节律）和年周期保持同步。植物和动物通常会对这些节律进行微小的调整，通常由光的强度触发，以使它们的内部时钟与季节的流逝或环境的变化同步。事实上，精确定时的强光爆发可以停止人类生物钟的日常循环。一个主要的问题是光信号是如何转化为生理反应的。大脑中的两个结构已被确定在这种反应中起作用，它们是下丘脑的视交叉上核和松果体。当视网膜受到光的刺激时，这些结构接收来自视网膜的神经输入。有人提出，一些脊椎动物也可能拥有松果体外、视网膜外的光感受器，称为深部脑光感受器，它们能够控制昼夜节律。目前我们还不知道这些假定的受体的位置、敏感性，最重要的是它们的神经连接。该项目授予Deviche博士一笔小额赠款，用于解决这一重要问题的探索性研究。他在一种高度光周期的北极鸟类身上发现了一个模型系统，可能会提供答案。利用一种能识别视网膜和松果体中视紫红质样光色素的抗体，他将定位大脑中的细胞体和终端。光照条件将被控制，以确定光照是否刺激这些脑细胞中这些光色素的表达。如果成功，这将首次证明中枢神经系统深处的一些细胞是光敏的。这些结果将为理解光刺激到达和改变神经系统以影响生物时间的机制开辟新的途径，并将对神经科学以外的北极生物学和鸟类学产生影响。了解生物钟的基本神经机制可以帮助我们治疗一些问题，比如在白天到晚上轮班工作时影响人类表现的注意力受损，或者时差，或者其他导致生物钟与环境不同步的因素。＊＊＊

9315307 Deviche It is well established that a wide variety of organisms have internal biological clocks that are instrumental in allowing them to maintain synchrony to both daily (i.e., circadian) and annual cycles of environmental change. Plants and animals routinely experience small adjustments in these rhythms, often triggered by intensity of light, to synchronize their internal clocks with the passing seasons or changes in the environment. Indeed, precisely timed bursts of bright light can stop the daily cycle of the human biological clock. A major question is how photic signals are transduced into physiological responses. Two structures in the brain that have been identified as playing a role in this response are the suprachiasmatic nuclei of the hypothalamus and the pineal gland. These structures receive neural input from the retina of the eye when it is stimulated by light. It has been proposed that some vertebrates also may possess extra-pineal, extra-retinal photoreceptors, referred to as deep brain photoreceptors, which are capable of entraining circadian rhythms. At this time we do not know the location, sensitivity, or most importantly the neural connections of these putative receptors. This project awards Dr. Deviche a small grant for exploratory resesarch to address this important problem. He has found a model system in a species of highly photoperiodic arctic bird that possibly could provide the answers. Using an antibody that identifies rhodopsin-like photopigments in the retina and the pineal, he will locate cell bodies and terminals in the brain. Light conditions will be manipulated to determine whether light exposure stimulates the expression of these photopigments in these brain cells. If successful, this will be the first demonstration that some cells deep within the central nervous system are photosensitive. These results would open new avenues towards understanding the mechanisms by which light stimulation reaches and alters th e nervous system to influence biological timing, and will have impact also beyond neuroscience to arctic biology and ornithology. Understanding the basic neural mechanisms for timing could lead to treatment of problems such as impaired attentiveness that affect human performance during work shifts from day to night, or jet lag, or other factors that make the internal clock out of sync with the environment. ***