CYCLIC NEUROPEPTIDES. “The timing of normal hypocretin/orexin production is critical as it contributes to staying awake (in humans typically later in the day) as sleep debt increases. In both humans and animals, absolute orexin deficiency is linked to the narcolepsy-cataplexy syndrome, while in animals a lack of orexin signaling increases risk of obesity.”
http://www.biomedcentral.com/1741-7015/11/79