title: Nociceptin/orphanin FQ up-regulates P2X₃ receptors in primary cultures of neonatal rat trigeminal ganglion neurons.
abstract: Recent evidence indicates a nociceptive role of the nociceptin/orphanin FQ-opioid receptor-like receptor (N/OFQ-ORL1) system in craniofacial pain; however, the mechanisms of such an effect remain unclear. We investigated whether the action of N/OFQ involves the modulation of P2X3 , a pain-transducing ionotropic receptor. Double-labeled immunohistochemical staining was used to determine the co-localization of ORL1 and P2X3 receptors in the trigeminal ganglia (TG) of neonatal Sprague-Dawley rats. The effect of N/OFQ (at a concentration ranging from 1 pM to 10 nM) on the expression of P2X3 receptors was detected by RT-PCR, western blotting, and immunocytochemical staining. We found that ORL1 receptors were co-localized with P2X3 receptors and that the application of N/OFQ could up-regulate, in a concentration-dependent manner, the expression of P2X3 receptor mRNA and P2X3 receptor protein in TG neurons. Immunocytochemical staining also revealed enhanced P2X3 immunoreactivity beneath the neuronal membrane and an increased percentage of P2X3 -positive neurons after treatment with N/OFQ. Those effects were completely blocked by a specific ORL1 antagonist, UFP-101. Our results suggest that the activation of ORL1 receptors by N/OFQ can potentiate P2X3 receptors in primary cultures of neonatal trigeminal neurons, which may be a mechanism for the nociceptive role of N/OFQ in the modulation of craniofacial pain. Our findings may also have implications in treating craniofacial pain.
authors.affiliation: State Key Laboratory of Oral Diseases and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Oral Diseases and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Hu
authors.initials: H
authors.lastname: Long
authors.affiliation: State Key Laboratory of Oral Diseases and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Jian
authors.affiliation: State Key Laboratory of Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Li
authors.affiliation: State Key Laboratory of Oral Diseases and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Oral Diseases and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Zhihe
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Oral Diseases and Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Wenli
authors.initials: W
authors.lastname: Lai
mesh_terms: D000818:Animals; D009474:Neurons; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D058477:Receptors, Purinergic P2X3; D012668:Trigeminal Ganglion
chemical_list: D012333:RNA, Messenger; D058477:Receptors, Purinergic P2X3
keywords: P2X3 receptor; craniofacial pain; nociceptin/orphanin FQ; opioid receptor-like receptor 1; trigeminal ganglion