Prepro-orexin is 130 amino acid long peptide with a putative 33 AA secretory sequence, a hydrophobic core followed by residues with small polar side chains. The expression was detected in brain and to a small extent in testis. These neuropeptides bind and activate two closely related Orexin receptorsG-protein coupled receptors (GPCRs) OX1R and OX2R. Orexins (Orexin A and Orexin B) are a family of hypothalamic neuropeptides selectively expressed in the hypothalamus. Orexin A and Orexin B are derived from the same precursor (Prepro-orexin) by proteolytic cleavage.