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Review

Nature Reviews Neuroscience 8, 171–181 (1 March 2007) | doi:10.1038/nrn2092

The neural circuit of orexin (hypocretin): maintaining sleep and wakefulness

Takeshi Sakurai

Sleep and wakefulness are regulated to occur at appropriate times that are in accordance with our internal and external environments. Avoiding danger and finding food, which are life-essential activities that are regulated by emotion, reward and energy balance, require vigilance and therefore, by definition, wakefulness. The orexin (hypocretin) system regulates sleep and wakefulness through interactions with systems that regulate emotion, reward and energy homeostasis.