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The orexin receptor (also referred to as the hypocretin receptor) is a G-protein-coupled receptor that binds the neuropeptide orexin. There are two variants, OX1 and OX2, each encoded by a different gene (, ). Both orexin receptors exhibit a similar pharmacology - the 2 orexin peptides, orexin-A and orexin-B, bind to both receptors and, in each case, agonist binding results in an increase in intracellular calcium levels. However, orexin-B shows a 10-fold selectivity for orexin receptor type 2, whilst orexin-A is equipotent at both receptors. Several orexin receptor antagonists are in development for potential use in sleep disorders. Only the crystal structure of OX2 is known. == Selective ligands == Several drugs acting on the orexin system are under development, either orexin agonists for the treatment of conditions such as narcolepsy, or orexin antagonists for insomnia. No non-peptide agonists are yet available, although synthetic Orexin-A polypeptide has been made available as a nasal spray and tested on monkeys. Several non-peptide antagonists are in development however; SB-649,868 by GlaxoSmithKline for sleep disorders is a non-selective orexin receptor antagonist. Another dual orexin antagonist, almorexant(ACT-078573) by Actelion, was abandoned because of side effects. A third entry is Merck's suvorexant (Belsomra), which has recently been approved for use. A new antagonist compound, ACT-462206, was recently studied in humans. Most ligands acting on the orexin system so far are polypeptides modified from the endogenous agonists Orexin-A and Orexin-B, however there are some subtype-selective non-peptide antagonists available for research purposes. * SB-334,867 – selective OX1 antagonist * SB-408,124 – selective OX1 antagonist * TCS-OX2-29 – selective OX2 antagonist * EMPA(drug) (N-Ethyl-2-()-N-pyridin-3-ylmethyl-acetamide) – selective OX2 antagonist * RTIOX-276 – selective OX1 antagonist 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Orexin receptor」の詳細全文を読む スポンサード リンク
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