“…In addition to the POA, sleeppromoting neurons have also been observed in other brain regions. For example, activation of gamma aminobutyric acid (GABA)ergic neurons in the parafacial zone (Anaclet et al, 2014), the ventrolateral periaqueductal gray (Weber et al, 2015;Weber et al, 2018), the ventral tegmental area (VTA) (Yang et al, 2018;Yu et al, 2019), or adenosine A 2A receptor-expressing neurons in the striatum (Oishi et al, 2017;Yuan et al, 2017) specifically promotes non-rapid eye movement (NREM) sleep, whereas subgroups of GABAergic neurons in the lateral hypothalamus (Jego et al, 2013;Konadhode et al, 2013;Tsunematsu et al, 2014) and the zona incerta (Liu et al, 2017) promote both REM and NREM sleep. With the exception of nitrergic/ glutamatergic neurons in the median and medial preoptic area that are excited by external warmth (Harding et al, 2018), the vast majority of sleep-promoting neuronal populations are GABAergic, and their sleep-promoting effects are likely mediated by the inhibition of wake-promoting populations.…”