title: Changes in spinal cord expression of fractalkine and its receptor in a rat model of disc herniation by autologous nucleus pulposus.
abstract: METHODS
  Behavior, mRNA and immunohistochemical assessment of the expression of fractalkine (CX3CL1) and its receptor (CX3CR1) in a rat model of disc herniation by autologous nucleus pulposus (NP) implantation.
  
  
  OBJECTIVE
  To evaluate the changes in expression of fractalkine and its receptor in the spinal cord and their association with pain behavior in a rat model of disc herniation.
  
  
  BACKGROUND
  Chemokines have recently been implicated in the pathophysiology of neuropathic pain. They mediate astrocytic migration and microglial proliferation, which are involved in the regulation of nociceptive transmission. Fractalkine is a chemokine, which participates in the mechanisms of neuropathic pain as a mediator of neuron-glia interactions.
  
  
  METHODS
  Sixty-six rats (NP-treated = 47, sham = 19) were implanted with autologous NP (approximately 3 mg) on the left L5 nerve root, just proximal to the dorsal root ganglion and tested for thermal hyperalgesia and mechanical allodynia before surgery and on days 1, 5, 10, 20, and 30 after surgery. The changes of expression of fractalkine and its receptor in the spinal cord were studied using real time PCR and immunohistochemistry.
  
  
  RESULTS
  Rats developed ipsilateral mechanical allodynia at day 1 and bilateral thermal hyperalgesia at day 5 after surgery, and these changes in sensitivity persisted throughout the observation period. The expression of mRNA for fractalkine in the spinal cord was increased by day 5 and remained upregulated for the duration of the experiment. The immunostaining for fractalkine increased in neurons and astrocytes and that for the fractalkine receptor increased in microglia in the dorsal horn ipsilateral to the disc herniation.
  
  
  CONCLUSIONS
  Our results indicate that autologous implantation of NP induces thermal hyperalgesia and mechanical allodynia, and leads to an upregulation of fractalkine and its receptor in spinal neurons and glia, implicating fractalkine in association with radicular pain.
authors.affiliation: Department of Rehabilitation Medicine, School of Medicine, Catholic University of Daegu, Daegu, Korea.
authors.forename: Hea-Woon
authors.initials: HW
authors.lastname: Park
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Ahn
authors.forename: Su-Jeong
authors.initials: SJ
authors.lastname: Kim
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Seo
authors.forename: Yun-Woo
authors.initials: YW
authors.lastname: Cho
authors.forename: Sung-Ho
authors.initials: SH
authors.lastname: Jang
authors.forename: Se-Jin
authors.initials: SJ
authors.lastname: Hwang
authors.forename: So-Young
authors.initials: SY
authors.lastname: Kwak
mesh_terms: D000818:Animals; D000073883:CX3C Chemokine Receptor 1; D054428:Chemokine CX3CL1 / Q000096:biosynthesis* / Q000235:genetics; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D006930:Hyperalgesia / Q000378:metabolism / Q000503:physiopathology; D007403:Intervertebral Disc / Q000637:transplantation*; D007405:Intervertebral Disc Displacement / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008159:Lumbar Vertebrae / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D018121:Receptors, Cytokine / Q000096:biosynthesis* / Q000235:genetics; D015728:Receptors, HIV / Q000096:biosynthesis* / Q000235:genetics; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D014182:Transplantation, Autologous
chemical_list: D000073883:CX3C Chemokine Receptor 1; D054428:Chemokine CX3CL1; D018121:Receptors, Cytokine; D015728:Receptors, HIV