Hypothalamic circuitry underlying stress-induced insomnia and peripheral immunosuppression

The neural substrates of insomnia/hyperarousal induced by stress remain unknown. Here, we show that restraint stress leads to hyperarousal associated with strong activation of corticotropin-releasing hormone neurons in the paraventricular nucleus of hypothalamus (CRHPVN) and hypocretin neurons in the lateral hypothalamus (HcrtLH). CRHPVN neurons are quiescent during natural sleep-wake transitions but are strongly active under restraint stress. CRISPR-Cas9-mediated knockdown of the crh gene in CRHPVN neurons abolishes hyperarousal elicited by stimulating LH-projecting CRHPVN neurons. Genetic ablation of Hcrt neurons or crh gene knockdown significantly reduces insomnia/hyperarousal induced by restraint stress. Given the association between stress and immune function, we used single-cell mass cytometry by time of flight (CyTOF) to analyze peripheral blood and found extensive changes to immune cell distribution and functional responses during wakefulness upon optogenetic stimulation of CRHPVN neurons. Our findings suggest both central and peripheral systems are synergistically engaged in the response to stress via CRHPVN circuitry.