Orexin, also known as hypocretin, is a neurotransmitter that is produced by a group of neurons located in the hypothalamus of the brain. Orexin is involved in the regulation of various functions, including wakefulness, feeding behavior, and energy homeostasis. Deficiencies or disruptions in the orexin system have been linked to several sleep disorders, such as narcolepsy, as well as obesity and other metabolic disorders. The role of orexin in the regulation of wakefulness and sleep is complex, but it is generally believed that orexin promotes wakefulness by inhibiting the activity of sleep-promoting neurons in the hypothalamus, including the VLPO (Ventrolateral Preoptic Nucleus).
