Orexin neurons in the lateral hypothalamus innervate and excite many wake-promoting brain regions

Targets of the orexin-producing neurons include monoaminergic areas such as the locus coeruleus, raphe nuclei, ventral tegmental area, periaqueductal grey, and tuberomammillary nucleus as well as cholinergic areas such as the basal forebrain and pedunculopontine and laterodorsal tegmental nuclei (PPT/LDT). Increased activity in these monoaminergic areas promotes wakefulness, inhibits REM sleep, and suppresses REM sleep-related phenomena including cataplexy.