Neural circuitry of the suprachiasmatic nucleus and retrochiasmatic area regulating arousal

The suprachiasmatic nucleus (SCN) and retrochiasmatic area (RCA) innervate the paraventricular nucleus of hypothalamus (PVH) that projects to the brainstem arousal parabrachial nucleus (PB), which may form a neural circuit regulating arousal, independent from the circadian control circuit of arousal. To test the hypothesis, we used DREADDs (Designer Receptors Exclusively Activated by Designer Drugs) to activate these regions and examine wakefulness. We found that chemo-stimulation of the PVH, the SCN, the RCA, and the PVH-PB pathway all significantly promoted wakefulness, suggesting that a neural circuit consisting of these nodes regulating arousal.