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. ***
