title: Changes in pain behavior and glial activation in the spinal dorsal horn after pulsed radiofrequency current administration to the dorsal root ganglion in a rat model of lumbar disc herniation: laboratory investigation.
abstract: OBJECTIVE
  Herniated discs can induce sciatica by mechanical compression and/or chemical irritation caused by proinflammatory cytokines. Using immunohistochemistry methods in the dorsal horn of a rat model of lumbar disc herniation, the authors investigated the effects of pulsed radiofrequency (PRF) current administration to the dorsal root ganglion (DRG) on pain-related behavior and activation of microglia, astrocytes, and mitogen-activated protein kinase.
  
  
  METHODS
  A total of 33 Sprague-Dawley rats were randomly assigned to either a sham-operated group (n = 10) or a nucleus pulposus (NP)-exposed group (n = 23). Rats in the NP-exposed group were further subdivided into NP exposed with sham stimulation (NP+sham stimulation, n = 10), NP exposed with PRF (NP+PRF, n = 10), or euthanasia 10 days after NP exposure (n = 3). The DRGs in the NP+PRF rats were exposed to PRF waves (2 Hz) for 120 seconds at 45 V on postoperative Day 10. Rats were tested for mechanical allodynia 10 days after surgery and at 8 hours, 1 day, 3 days, 10 days, 20 days, and 40 days after PRF administration. Immunohistochemical staining of astrocytes (glial fibrillary acidic protein), microglia (OX-42), and phosphorylated extracellular signal-regulated kinases (pERKs) in the spinal dorsal horn was performed at 41 days after PRF administration.
  
  
  RESULTS
  Starting at 8 hours after PRF administration, mechanical withdrawal thresholds dramatically increased; this response persisted for 40 days (p < 0.05). After PRF administration, immunohistochemical expressions of OX-42 and pERK in the spinal dorsal horn were quantitatively reduced (p < 0.05).
  
  
  CONCLUSIONS
  Pulsed radiofrequency administration to the DRG reduced mechanical allodynia and downregulated microglia activity and pERK expression in the spinal dorsal horn of a rat model of lumbar disc herniation.
authors.affiliation: Department of Physical Medicine and Rehabilitation, College of Medicine, Yeungnam University, Daegu, Republic of Korea.
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Cho
authors.forename: Yun Woo
authors.initials: YW
authors.lastname: Cho
authors.forename: Eun Hyuk
authors.initials: EH
authors.lastname: Kim
authors.forename: Menno E
authors.initials: ME
authors.lastname: Sluijter
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Hwang
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Ahn
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000503:physiopathology*; D006930:Hyperalgesia / Q000209:etiology / Q000503:physiopathology; D007405:Intervertebral Disc Displacement / Q000503:physiopathology / Q000628:therapy*; D008159:Lumbar Vertebrae / Q000601:surgery; D008297:Male; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D061208:Pulsed Radiofrequency Treatment / Q000295:instrumentation / Q000379:methods*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors