Orexin and melanin-concentrating hormone neurons: a hypothalamic interface for sleep and feeding regulation

Orexin and melanin-concentrating hormone (MCH) neurons reside in the lateral hypothalamic area (LHA) and regulate sleep and feeding behaviour in mammals. In rodents, orexin neurons are implicated in the regulation of wakefulness or palatable con- sumption, whereas MCH neurons are implicated in the regulation of rapid eye movement sleep episode duration or caloric con- sumption. This review explores the molecular, genetic and neuronal components of orexin and MCH signalling as mediators of arousal state transitions. These peptidergic signalling systems, which interconnect both with sleep centres in the LHA and feed- ing centres in the arcuate nucleus, may maintain the balance between sleep need and duration with hunger and food foraging.