Fig. 2
From: Role of GABA in the regulation of the central circadian clock of the suprachiasmatic nucleus
Schematic diagram of circadian organization in the SCN. Light input is transmitted to the ventral SCN through the retinohypothalamic tract (RHT). Several neuropeptides are expressed in the SCN and almost all SCN cells are GABAergic neurons. Circadian rhythms in individual SCN cells synchronize via neurotransmitters, and synchronized circadian rhythms in the SCN regulate behaviors such as sleep and wake cycles