[Ala11, D-Leu15]-Orexin B is a highly potent and selective OX2 receptor agonist with 400-fold selectivity for OX2 over OX1 receptors, possessing EC50 values of 0.13 and 52 nM for human OX2 and OX1 receptors respectively. [Ala11,D-Leu15]-Orexin B increase