Abstract

Most biological processes exhibit circadian rhythms that are synchronized by the master clock located in the suprachiasmatic nucleus (SCN). Recently, cells in the oval nucleus of the bed nucleus of the stria terminalis (OV-BNST), the central nucleus of the amygdala (CEA), basolateral amygdala (BLA) and dentate gyrus of the hippocampus (DG), have been shown to rhythmically express Period 2 (PER2), a clock protein. It is known that gonadal hormones have an effect on circadian rhythms. However, yet to be determined is what influence they might have on brain circadian oscillators outside of the SCN. The purpose of this series of experiments is to examine PER2 expression; firstly, in intact females over the course of the estrous cycle and, secondly, in gonadectomized females, males, and intact males. Results obtained from the intact females suggest that the pattern of PER2 expression in the OV-BNST and the CEA changes as a function of stage of the estrous cycle. In ovariectomized females peak PER2 expression in the OV-BNST and CEA is at ZT13, the same was also found in gonadectomized and intact males. Together, the data from these studies suggest that gonadal hormones may influence the circadian functioning of these two brain regions.