Circadian influence on neurons of the substantia nigra

Abstract

Circadian rhythms, such as body temperature, hormone secretion, sleep/wake, and activity/rest, are generated by the oscillation of the clock genes in the cells of the suprachiasmatic nucleus, thus considered the main circadian oscillator. Dopamine, whose synthesis occurs in centers such as the substantia nigra pars compacta (SNc) can influence autonomic oscillation. Dopamine can modulate the expression of clock genes; meanwhile, the presence of clock genes in this area could indicate a cyclic mechanism in dopamine-producing cells. Although the involvement of SNc in motor and non-motor functions is well known, the role of the circadian system in this region is not clear. In this study, we investigated the presence of Per1, Per2, and Cry1 in dopaminergic neurons of the SNc. Per1, Per2, and Cry1 imunorreactivity were analyzed at specific times of the light-dark phase by immunohistochemistry technique in a diurnal primate. The mapping performed by immunohistochemistry showed expressive Per1-IR with predominance during daytime. The Per2-IR and Cry1-IR were similar between the light and dark times analyzed. These results reinforce the presence of proteins that regulate circadian rhythms in the SNc, an important dopaminergic source.