Abstract
Cell bodies in the rat suprachiasmatic nucleus (SCN) were labeled with an antibody against a small domain of the period (per) protein, the product of a gene in Drosophila that regulates circadian rhythms. In immunoblots of SCN protein extracts, the antibody recognized a band of approximately 115 kD, as well as a heterogeneous antigen ranging from 160 kD to 170 kD. The antibody was found in previous studies to label putative circadian pacemaker neurons in Aplysia and Bulla, as well as the cellular sites of per expression in flies. Taken together, these results suggest that the region of the per protein recognized by this antibody may be widely conserved in neuronal circadian pacemakers.