Orexin Receptor (OX Receptor) (食欲素受体)

The orexin receptors (hypocretin receptors) are a family of G protein-coupled receptors and consist of orexin receptor 1 (OX1R) and orexin receptor 2 (OX2R) subtypes. Orexin receptors are expressed throughout the central nervous system and are involved in the regulation of the sleep/wake cycle.

Orexin A binding to OX1R and OX2R with similar affinity, and orexin B binding to OX2 with higher affinity than OX1R. OX1R is mainly expressed in the prefrontal and infralimbic cortex, hippocampus, paraventricular thalamic nucleus, and locus coeruleus. OX2R is mainly distributed in the cerebral cortex, septal nuclei, lateral hypothalamus, hippocampus, and hypothalamic nuclei.

Both OX1R and OX2R are coupled via G_q/11 to the activation of phospholipase C, leading to an elevation of intracellular Ca²⁺ levels. Moreover, OX2R also couples via G_s and G_i/o to the cAMP pathways.