Sleep, feeding, and neuropeptides: roles of orexins and orexin receptors.

Recent studies using molecular genetics in mice and dogs, as well as histopathological analyses of human disease, have come to the same conclusion: the human sleep disorder narcolepsy is caused by failure of signaling mediated by orexin (hypocretin) neuropeptides. These and other findings strongly suggest that the orexin system plays a critical role in sleep/wake regulation. In addition, the orexin system may link energy homeostasis to the regulation of sleep/wake cycles.