title: [Orexins and pain processing].
abstract: Orexin-A and orexin-B are hypothalamic peptides and regulate feeding behavior, energy metabolism and the sleep-wake cycle. Orexin-A binds equally to both orexin-1 and orexin-2 receptors, while orexin-B has a preferential affinity for orexin-2 receptors. Orexin-A and orexin-B are concentrated in superficial laminae of the spinal dorsal horn, and orexin-A and orexin-1 receptors are found in the dorsal root ganglion cells. Intravenous injection of orexin-A produces an anti-thermal hyperalgesic effect in the carrageenan test and this effect of orexin-A was mediated by the activation of orexin-1 receptor at the peripheral primary afferent terminal. Intrathecal and intracerebroventricular injection of orexin-A produces an analgesic effect in the formalin test and the carrageenan test and the neuropathic pain models and these effects of orexin-A are thought to be mediated by the activation of orexin-1 receptor. In the isolated spinal cord preparation from 0-to 3-day old rats, a slow depolarizing response induced by single shock stimulation of a dorsal root at C-fiber strength and wind-up phenomenon were effectively attenuated by the application of orexin-A, orexin-B and [Ala11 D-Leu15] orexin-B, a selective orexin-2 receptor agonist. This suggested that, in the neonatal rat spinal cord, orexin-2 receptor, but not orexin-1 receptor, is involved in the nociceptive transmission.
authors.affiliation: Department of Anesthesiology, Graduate School of Medicine, Chiba University, Chiba 260-8670.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Koyo
authors.initials: K
authors.lastname: Shono
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000188:drug therapy; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology / Q000502:physiology* / Q000627:therapeutic use; D009479:Neuropeptides / Q000494:pharmacology / Q000502:physiology* / Q000627:therapeutic use; D064446:Orexin Receptors; D000068797:Orexins; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000502:physiology*; D018013:Receptors, Neuropeptide / Q000819:agonists / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide