Introduction: Two neuropeptides,orexin-A and orexin-B,are implicated in modulating neuronal firing,sleep/wake regulation,feeding behaviors by activating two orphan G-protein-coupled receptors: orexin 1 and orexin 2 receptors(OX1R and OX2R).While the expression of orexins and orexin receptors is immunohistochemically revealed in retinal neurons,the function of these peptides in the retina is largely unknown.