Hypocretin Receptor 1 (HCRTR1)

R) is one of two receptors that recognize the peptide neurotransmitters orexin A and orexin B. Orexin A and B are 33 and 28 amino acids in length, respectively, and are derived from a common precursor termed prepro-orexin. OX₁R binds orexin A with greater affinity than orexin B (a one order of magnitude difference), while OX₂R binds both ligands with similar affinities.Both OX₁R and OX₂R belong to the 7-transmembrane domain, G protein-coupled receptor (GPCR) superfamily. OX₁R is thought to transmit signals through the Ga₁₁ class of G proteins, resulting in the activation of phospholipase C with subsequent triggering of the phosphatidylinositol cascade and an influx of extracellular Ca²⁺, probably through transient receptor potential (TRP) channels.