title: Up-regulation of acid-sensing ion channel 3 in dorsal root ganglion neurons following application of nucleus pulposus on nerve root in rats.
abstract: METHODS
  Immunocytochemistry for acid-sensing ion channel 3 (ASIC3) in neurons of rat dorsal root ganglions (DRGs) from animals exposed to a model of lumbar disc herniation.
  
  
  OBJECTIVE
  To examine expression of ASIC3 in DRGs and the effect of a sodium channel blocker applied to the nerve root in a rat model of lumbar disc herniation.
  
  
  BACKGROUND
  Radicular pain is a common symptom of lumbar disc herniation in human beings. A depolarizing sodium channel gated by protons during tissue acidosis, ASIC3, is specifically expressed in sensory neurons. It has been associated with cardiac ischemic and inflammatory pain. We often perform spinal nerve root block for radicular pain using a sodium channel blocker, such as lidocaine; however, it has been unclear whether the effective period of this treatment is usually longer than the expected duration of efficacy.
  
  
  METHODS
  For the lumbar disc herniation model, nucleus pulposus was harvested from the tail and applied to the L5 nerve root, and the nerve roots were pinched. We evaluated mechanical allodynia in sham-operated animals and a disc herniation model. Immunohistochemistry was used to examine ASIC3 expression in L5 DRGs. Finally, the effect of lidocaine on pain and ASIC3 expression in the disc herniation model was examined.
  
  
  RESULTS
  Animals exposed to the lumbar disc herniation model showed allodynia for 8 days, and ASIC3 immunoreactivity was up-regulated in DRG neurons. After administration of lidocaine to spinal nerve roots affected by disc herniation, ASIC3 immunoreactivity was down-regulated in DRG neurons, and the level of mechanical allodynia was significantly decreased for 8 days.
  
  
  CONCLUSIONS
  Our results suggest that ASIC3 in DRG neurons may play an important role in nerve root pain caused by lumbar disc herniation. Lidocaine decreased ASIC3 expression in DRG neurons and pain associated with the disc herniation model.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan. sohtori@faculty.chiba-u.jp
authors.forename: Seiji
authors.initials: S
authors.lastname: Ohtori
authors.forename: Gen
authors.initials: G
authors.lastname: Inoue
authors.forename: Takana
authors.initials: T
authors.lastname: Koshi
authors.forename: Toshinori
authors.initials: T
authors.lastname: Ito
authors.forename: Hideo
authors.initials: H
authors.lastname: Doya
authors.forename: Tomoko
authors.initials: T
authors.lastname: Saito
authors.forename: Hideshige
authors.initials: H
authors.lastname: Moriya
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D062565:Acid Sensing Ion Channels; D000818:Animals; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology*; D006930:Hyperalgesia / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D007403:Intervertebral Disc / Q000473:pathology* / Q000637:transplantation; D007405:Intervertebral Disc Displacement / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000378:metabolism*; D013126:Spinal Nerve Roots / Q000187:drug effects / Q000473:pathology*; D015854:Up-Regulation
chemical_list: C568269:ASIC3 protein, rat; D062565:Acid Sensing Ion Channels; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D015222:Sodium Channels; D008012:Lidocaine