Orexin Receptors

Orexin receptors (OX1 and OX2) and their cognate peptides (orexin-A and-B) were discovered in 1998, and were soon thereafter found to regulate feeding and sleep/wakefulness. Orexins and orexin receptors are found in the central nervous system and in the periphery, although their physiological functions outside the brain remain poorly defined. Although orexins are brain neurotransmitters, they may serve as endo- or paracrine mediators in the periphery. The expression pattern of either receptor subtype (OX1, OX2) is not easily connected to particular physiological functions. Gene deletion and pharmacologic studies suggest the physiological functions of these receptor subtypes may be overlapping. In genetically narcoleptic dogs, the OX2 receptor protein is nonfunctional …