Effect of repeated electroacupuncture on the expression of NR2B subunit of N-methyl-D-aspartate receptor in the spinal cord of rats with chronic constrictive injury

Objective:To observe the effect of repeated electroacupuncture(EA) on the expression of NR2B subunit of NMDA receptor in the lumbar spinal cord in rats with chronic constrictive injury(CCI) pain,so as to analyze the analgesic mechanism of repeated acupuncture.Method:A total of 50 Wistar rats were randomized into control,CCI model,EA 3 times,EA 5 times and EA 10 times groups,with 10 cases in each group.CCI pain model was established by loosely ligating the sciatic nerve near the proximal and of the bifid site.The animals' paw withdrawal latency(PWL) of radiant heat irradiation was recorded before EA everyday.The difference values between the affected limb and the healthy limb were used to judge the changes of pain threshold.EA(2/15Hz,1mA) was respectively applied to bilateral Zusanli(ST36)-Yanglingquan(GB34) for 30 min,once daily for EA 3 times,EA 5 times and EA 10 times groups respectively.The spinal cord tissues of the L2—6 segments were removed for detecting the expressions of NR2B mRNA and protein of NR2B receptor with reversed transcription-polymerase chain reaction(RT-PCR) and Western blotting techniques separately.Result:In comparison with control group,PWL difference value of CCI,EA 3 times,EA 5 times,EA 10 times groups increased significantly(P0.01),suggesting a marked decrease of pain threshold.Compared with CCI group,PWLs of EA 5 times and EA10 times decreased significantly(P0.01),showing a better cumulative analgesic effect.At the same time,the NR2B mRNA and protein levels decreased with the increasing times of EA.Conclusion:The levels of NR2B subunit in spinal cord of rats with neuropathic pain were higher,which may be one of the causes of neuropathic pain and NR2B subunit involved in the accumulative effect of EA in the rat with CCI.