GABA neurons in the ventral tegmental area regulate non-rapid eye movement sleep in mice.

Sleep/wakefulness cycle is regulated by coordinated interactions between sleep- and wakefulness-regulating neural circuitry. However, the detailed mechanism is far from understood. Here, we found that glutamic acid decarboxylase 67-positive GABAergic neurons in the ventral tegmental area (VTA) are a key regulator of non-rapid eye movement (NREM) sleep in mice. VTA project to multiple brain areas implicated in sleep/wakefulness regulation such as the lateral hypothalamus (LH). Chemogenetic activation of VTA promoted NREM sleep with higher delta power whereas optogenetic inhibition of these induced prompt arousal from NREM sleep, even under highly somnolescent conditions, but not from REM sleep. VTA showed the highest activity in NREM sleep and the lowest activity in REM sleep. Moreover, VTA directly innervated and inhibited wake-promoting orexin/hypocretin neurons by releasing GABA. As such, optogenetic activation of VTA terminals in the LH promoted NREM sleep. Taken together, we revealed that VTA play an important role in the regulation of NREM sleep.