Central functions of the orexinergic system.

The neuropeptide orexin is synthesized by neurons exclusively located in the hypothalamus. However, these neurons send axons over virtually the entire brain and spinal cord and therefore constitute a unique central orexinergic system. It is well known that central orexin plays a crucial role in the regulation of various basic non-somatic and somatic physiological functions, including feeding, energy homeostasis, the sleep/wake cycle, reward, addiction, and neuroendocrine, as well as motor control. Moreover, the absence of orexin results in narcolepsy-cataplexy, a simultaneous somatic and non-somatic dysfunction. In this review, we summarize these central functions of the orexinergic system and associated diseases, and suggest that this system may hold a key position in somatic-non-somatic integration.