电针对慢性压迫性损伤大鼠脊髓N-甲基-D-天门冬氨酸受体NR2B表达的影响

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

目的:观察电针对慢性压迫性损伤(CCI)大鼠脊髓N-甲基-D-天门冬氨酸受体NR2B表达的影响,分析电针(EA)累积性镇痛效应可能的作用机制。方法:将50只Wistar大鼠随机分为正常对照组、CCI模型组、EA3次组、EA5次组、EA10次组,每组10只。对照组大鼠行假手术,其余4组结扎坐骨神经造成CCI疼痛模型。手术后一周开始测定大鼠双侧缩腿的潜伏期(PWL)。EA3次组于CCI术后第14天电针双侧"足三里"-"阳陵泉"连续3d,EA5次组于CCI术后第12天电针双侧"足三里"-"阳陵泉"连续5d,EA10次组于CCI术后第7天电针双侧"足三里"-"阳陵泉"连续10d,每天1次。电针结束后用RT-PCR和Western blot法检测脊髓NMDA受体NR2B表达的情况。结果:与对照组比较,CCI后各组动物出现明显的痛觉过敏(P<0.01)。EA5次后动物的痛觉过敏有明显减轻。EA10次后动物的痛觉过敏进一步减轻。CCI后第18天大鼠脊髓NMDA受体NR2B亚基mRNA和蛋白表达水平明显增加,与CCI组,EA5次组和EA10次组比较NMDA受体NR2B亚基mRNA和蛋白表达水平明显下降(P<0.05)。结论:NR2B表达上调可能是神经损伤后出现慢性疼痛的发病机制之一,电针有可能通过抑制其表达从而发挥一定程度镇痛作用。

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, lmA） was respectively applied to bilateral ＂Zusanli＂（ST36）-＂Yan- glingquan＂（GB34） for 30 rain, 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 （P〈0.01）,suggesting a marked decrease of pain threshold. Compared with CCI group, PWLs of EA 5 times and EA10 times decreased significantly （P〈0.01）, 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.