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 A Peptide is 33 aa long corresponding to aa 34-66 of orexin precursor after cleavage into Orexin A and B.Bovine, Human, Mouse, Rat: pGlu-Pro-Leu-Pro-Asp-Cys-Cys-Arg-Gln-Lys-Thr-Cys-Ser-Cys-Arg-Leu-Tyr-Glu-Leu-Leu-His-Gly-Ala-Gly-Asn-His-Ala-Ala-Gly-Ile-Leu-Thr-Leu-NH2 (Cys6-Cys12, Cys7-Cys14) or pEPLPDCCRQKTCSCRLYELLHGAGNHAAGILTL-NH2 (Cys6-Cys12, Cys7-Cys14)