Orexin B is a hypothalamatic neuropeptide stimulating food intake in rats. Orexin B activates OX2 receptors. Both OX1 and OX2 receptors are involved in maintaining arousal. OX2 receptors appear to be inhibitory autoreceptors on orexin-containing neurons. Orexin B stimulates food consumption in a similar manner to orexin A, but the effect did not last as long as that of orexin A. The affinity of orexin B for the OX1 receptor is significantly lower than that of orexin A. Binding affinities for the OX2 receptor are similar for orexin A and B.