title: G protein-coupled receptor, family C, group 5 (GPRC5B) downregulation in spinal cord neurons is involved in neuropathic pain.
abstract: BACKGROUND
  G protein-coupled receptor, family C, group 5 (GPRC5B), a retinoic acid-inducible orphan G-protein-coupled receptor (GPCR), is a member of the group C metabotropic glutamate receptor family proteins presumably related in non-canonical Wnt signaling. In this study, we investigated altered GPRC5B expression in the dorsal horn of the spinal cord after spinal nerve injury and its involvement in the development of neuropathic pain.
  
  
  METHODS
  After induction of anesthesia by intraperitoneal injection of pentobarbital (35 mg /kg), the left L5 spinal nerve at the level of 2 mm distal to the L5 DRG was tightly ligated with silk and cut just distal to the ligature. Seven days after nerve injury, animals were perfused with 4% paraformaldehyde, and the spinal cords were extracted and post-fixed at 4℃ overnight. To identify the expression of GPRC5B and analyze the involvement of GPRC5B in neuropathic pain, immunofluorescence was performed using several markers for neurons and glial cells in spinal cord tissue.
  
  
  RESULTS
  After L5 spinal nerve ligation (SNL), the expression of GPRC5B was decreased in the ipsilateral part, as compared to the contralateral part, of the spinal dorsal horn. SNL induced the downregulation of GPRC5B in NeuN-positive neurons in the spinal dorsal horn. However, CNPase-positive oligodendrocytes, OX42-positive microglia, and GFAP-positive astrocytes were not immunolabeled with GPRC5B antibody in the spinal dorsal horn.
  
  
  CONCLUSIONS
  These results imply that L5 SNL-induced GPRC5B downregulation may affect microglial activation in the spinal dorsal horn and be involved in neuropathic pain.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kosin University College of Medicine, Busan, Korea.
authors.forename: Hyung-Joo
authors.initials: HJ
authors.lastname: Chung
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kosin University College of Medicine, Busan, Korea.
authors.forename: Ju Deok
authors.initials: JD
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Kosin University College of Medicine, Busan, Korea.
authors.forename: Kyung Han
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Na Young
authors.initials: NY
authors.lastname: Jeong
keywords: GPCR5B; Microglial activation; Neuroglial cell; Neuropathic pain; Spinal nerve injury
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