Pubertal Brain Development: Hormones & Circadian Entrainment

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Most species undergo at least two life phases, early growth followed by a mature reproductive stage. In mammals these phases are linked by a period of major physiological, neural and behavioral change defined as adolescence. Hormonal changes associated with maturation cause important changes in the brain and behavior. Little attention, however, has been paid to what happens during the period of adolescent change that is unique to that period. One of these changes is a delay in the timing of sleep/wake cycle that this project models in a slow-developing diurnal rodent, the degu, and a faster-developing common lab animal, the rat. This project will determine the role of adolescent hormone changes on the altered timing of the sleep/wake cycle by removing and replacing them. It will also determine whether the neural changes are occurring in the area of the brain that coordinates all daily rhythms, or if the changes are in areas that receive those central signals by examining slices of the tissue collected and analyzed around the clock. Lastly, the project will examine the impact of different lighting levels on the adolescent changes by examining changes in daily behavior under different conditions. Because changes in the daily timing mechanism of the brain impacts nearly all aspects of physiology, these findings will lead to a greater appreciation of the physiological and behavioral state of mammals during adolescence. The project will support the research activity of a graduate student and at least two undergraduates each year. The students and the project director also provide academic and community learning opportunities related to adolescent sleep/wake changes. The project will also support the development of a data base of daily activity and other rhythms collected from animals that can be shared with other researchers in the field.