Therapeutic Effect Of Electroacupuncture On Rats With Neuropathic Pain

Objective: To study the therapeutic effect and possible mechanism of electroacupuncture on rats with neuropathic pain (NP). Methods: A total of 30 Sprague Dawley rats were randomized into three groups, group A (n=10), group B (n=10), and group C (n=10). In group A, a chronic constriction injury (CCI) model of NP was induced by loosely making four ligations at the mid-thigh level of the right sciatic nerve of rats with 4-0 chromic catgut, and electroacupuncture was used at day 1, day 4 and day 7 after surgery respectively as the treatment of NP. In group B, the CCI model was also induced and no treatment was given. In group C, the same surgery was made without tying the sciatic nerve. The thermal and mechanical pain thresholds of each rat before surgery and from day 1 to 7 after surgery were recorded and compared. The rats were sacrificed on day 8 after surgery and underwent perfusion-fixation for the removal of spinal cord. Western blot was used to detect the expression of CX3CR1 protein in the spinal cord. Enzyme-linked immunosorbent assay was used to measure the levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin 6 (IL-6) in the spinal cord. Results: In group A, mechanical withdrawal thresholds (MWT) and paw withdrawal latency (PWL) of right hind paw on day 1-3 after surgery were significantly lower than those before surgery (P<0.05); MWT and PWL were significantly higher on day 4-7 after surgery than those on day 3 after surgery (P<0.05), but were still lower than the preoperative levels (P<0.05). In group B, MWT and PWL of right hind paw on day 1-7 after surgery were significantly lower than those before surgery (P<0.05). There were no significant differences in MWT and PWL of right hind paw between group A and group B on day 1-3 after surgery (P>0.05). MWT and PWL in group A were significantly higher than those in group B on day 4-7 after surgery (P<0.05). Compared with the preoperative levels, there were no significant differences in MWT and PWL in group C after surgery (P>0.05). Compared with those in group C, MWT and PWL of right hind paw in group A and group B declined significantly after surgery (all P<0.05); In group A and group B, no significant differences were found in MWT and PWL of left hind paw before and after surgery (all P>0.05). The expression of CX3CR1 protein was significantly increased in group A and group B compared with that in group C (all P<0.05), and the expression of CX3CR1 protein in group A was significantly lower than that in group B (P<0.05). The levels of TNF-alpha, IL-1 beta and IL-6 in group A and group B were significantly higher compared with those in group C (P<0.05). The levels of TNF-alpha, IL-1 beta and IL-6 in group A were significantly lower than those in group B (all P<0.05). Conclusion: The thermal and mechanical pain thresholds of CCI rats decrease significantly. Electroacupuncture can significantly relieve pain and increase pain threshold. The development of NP may be associated with the increase of the expression of CX3CR1 protein and the levels of inflammatory factors in the spinal cord, including TNF-alpha, IL-1 beta and IL-6. The mechanism of electroacupuncture as a treatment for NP may be related to the reduction of the expression of CX3CR1 protein and the levels of inflammatory factors.