what is orexin
Orexin, also called hypocretin, is a neuropeptide that regulates arousal, wakefulness, and appetite.The most common form of narcolepsy, in which the sufferer briefly loses muscle tone (cataplexy), is caused by a lack of orexin in the brain due to destruction of the cells that produce it.ogs that lack a functional receptor for orexin have narcolepsy, while animals and people lacking the orexin neuropeptide itself also have narcolepsy. Central administration of orexin-A strongly promotes wakefulness, increases body temperature and locomotion, and elicits a strong increase in energy expenditure.