Orexins are neuropeptides that play a significant role in the regulation of food intake and sleep-wakefulness, possibly by coordinating the complex behavioral and physiologic responses of these complementary homeostatic functions. A broader role in the homeostatic regulation of energy metabolism, autonomic function, hormonal balance and the regulation of body fluids, is also suggested. Mutations in orexin gene are a cause of narcolepsy 1 (NRCLP1) due to a deficient orexin system and low level of rexins in the brain and cerebrospinal fluid of narcoleptic patients. Orexin A binds to both orexin receptor type 1 and 2 (OX1R and OX2R) with a high affinity, whereas orexin B binds only to OX2R with a similar high affinity. Orexin B Peptide is 28 aa long corresponding to aa 70-97 of orexin precursor after cleavage into Orexin A and B.Human: H-Arg-Ser-Gly-Pro-Pro-Gly-Leu-Gln-Gly-Arg-Leu-Gln-Arg-Leu-Leu-Gln-Ala-Ser-Gly-Asn-His-Ala-Ala-Gly-Ile-Leu-Thr-Met-NH2 or H-RSGPPGLQGRLQRLLQASGNHAAGILTM-NH2