Suprachiasmatic nucleus (SCN)

The suprachiasmatic nucleus (SCN) is a small group of neurons located in the hypothalamus above the optic chiasm and serves as the master circadian pacemaker in mammals[1][2][7]. It regulates daily physiological and behavioral rhythms, including the sleep-wake cycle, hormone secretion (notably influencing the pineal gland to produce melatonin at night), body temperature, feeding, and various neurohormonal outputs[1][2][7]. The SCN receives light input from the retina via the retinohypothalamic tract, using neurotransmitters such as glutamate and PACAP, and uses both cell-autonomous transcriptional feedback loops and network signaling to generate and synchronize circadian rhythms throughout the body[1][2][3]. Disruption of the SCN leads to sleep and mood disorders[1]. While signaling molecules and receptors within the SCN (e.g., vasopressin, VIP, GABA, PAC1-R) may be drug targets, the SCN itself is not considered a direct molecular therapeutic target—it is a brain structure rather than a protein, enzyme, or receptor[1][2][3][5]. Thus, "Suprachiasmatic nucleus signaling" refers to a brain signaling pathway or brain region, not a canonical drug target.

Other names

Suprachiasmatic nuclei

Melatonin—acts via melatonin receptors to modulate signals from the SCN to regulate sleep-wake cycles