Fig. 3.

Regulation of core circadian oscillator in the SCN. In mammals, the core circadian oscillator is the feedback loop composed of Per/Cry and Clock/Bmal 1 heterodimers. These proteins create spontaneous circadian rhythms of their own expression essentially by transcriptional control. In addition, in order to adapt to internal and external conditions, the core circadian oscillator is regulated by numerous factors including environmental changes, hormones and neutritional signals, which are transmitted to the core circadian clock through signal transduction proteins that regulate the core oscillator by a variety of mechanisms such as phosphorylation.