Electroacupuncture Downregulates the Expression of Spinal Interleukin-6 Protein in Chronic Neuropathic Pain Rats

Objective: To investigate the effect of electroacupuncture(EA)on spinal interleukin-6(IL-6) protein expression in neuropathic pain rats.Methods: Twenty-four adult SD rats were evenly and randomly divided into sham-operation group,model group and EA group.Chronic constrictive injury(CCI) model was established by ligating the sciatic nerve with catgut under anesthesia(10% chloral hydrate,300 mg/kg).EA(2 Hz,1 mA) was applied to Weizhong(BL 40) and Huantiao(GB 30) for 30 min,once on the 1~st,4~th and 7~th day after operation separately.The mechanical(von Frey filaments) and thermal(heat radiation) pain thresholds were measured before operation and on the 7~th day after the operation.The expression of IL-6 in the spinal cord(L_4-5) tissues was assayed by immunohistochemical technique.Results: Before operation,no significant differences were found among the 3 groups in both mechanical pain threshold and thermal pain threshold of the bilateral hind-limbs(P0.05).In comparison with sham-operation group,after CCI,both the mechanical and thermal pain thresholds of model group on the affected hind-limb lowered significantly,appearing mechanical allodynia and thermal hyperalgesia.Compared with model group,the mechanical and thermal pain thresholds of EA group increased significantly after EA(P0.05).Correspondingly,the average optical density value of IL-6 immunoreactive(IR) positive cells in the ipsilateral spinal dorsal horn of model group was significantly higher than that of sham-operation group and EA group(P0.05).It indicated that EA could markedly suppress CCI-induced allodynia and hyperalgesia and increase of IL-6 expression in the spinal cord.Conclusion: EA analgesia may be related to its resultant downregulation of IL-6 expression in the dorsal horn of the spinal cord in neuropathic pain rats.