OXA (17-33) (Orexin A (17-33) (human, mouse, rat, bovine)) is the shortest active orexin peptide that selectively targets OX1 (EC50=8.29 nM), with 23-fold selectivity for the OX1 receptor over the OX2 receptor. The activity of OXA (17-33) depends on the Tyr17, Leu20, Asn25, His26 residues and the spatial conformation of the alpha-helix. OXA (17-33) activates signaling pathways involving inositol-1,4,5-trisphosphate receptor (IP3R), phospholipase D (PL-D) and choline-Sigma-1R, thereby increasing the cytoplasmic Ca2+ level in nucleus accumbens neurons, an effect that is blocked by Sigma-1R antagonists. OXA (17-33) serves as an important biological probe for investigating the function of the OX1 receptor. OXA (17-33) can be modified via incorporation of mixed disulfide bonds of homocysteine and cysteamine, and is widely used in studies related to insomnia and narcolepsy[1][2][3].
