Sequential Changes of CX3CR1 in Dorsal Root Ganglion in a Rat Model of Lumbar Disc Herniation

Abstract

Objective: To investigate the pain-related behaviors and the changes of CX3CR1 expression in the dorsal root ganglion (DRG) in a rat model of lumbar disc herniation. Method: A total of 90 male Sprague-Dawley rats were used. A laminectomy was performed to expose left L5 nerve roots and corresponding DRG. Autologous nucleus puplosus was implanted on the left L5 nerve root proximal to the DRG without mechanical compression. Sham operation was also done with the same procedure as mentioned above. Thermal hyperalgesia and mechanical allodynia were assessed at 1, 5, 10, 20 and 30 days after surgery. Real time PCR and immunohistochemistry after behavioral test were performed. Results: In the lumbar disc herniation rats, significant reduction of thermal withdrawal latency indicating thermal hyperalgesia was shown on the ipsilateral hindpaw on postoperative day 1 (p＜0.01) and peaked on day 10 (p＜0.05) and maintained throughout day 30 (p＜0.05). The reduction of mechanical allodynia threshold, indicating mechanical allodynia, was observed on the ipsilateral hindpaw on postoperative day 1 (p＜0.01) and continued throughout day 30 (p＜0.01). Real time PCR showed the decrease in mRNA expression of CX3CR1 in the ipsilateral DRG on day 1 (p＜0.05) and the significant increase on day 20 (p＜0.05). The immunoreactivity for CX3CR1 was also increased in ipsilateral DRG on day 10 and 20. Conclusion: These data suggest that lumbar disc herniation induces thermal hyperalgesia and mechanical allodynia and upregulates the expression of CX3CR1 in dorsal root ganglion. Expression of CX3CR1 might be associated with subacute neuropathic pain after intervertebral disc herniation.