海马一氧化氮/蛋白激酶G信号通路参与针刺对慢性痛大鼠产生的累积性镇痛效应

Involvement of Hippocampal NO/PKG Signaling Pathway in the Accumulative Analgesic Effect of Electroacupuncture Stimulation of "Zusanli"(ST 36)-"Yanglingquan"(GB 34) in Chronic Neuropathic Pain Rats

目的:观察慢性压迫性损伤(CCI)大鼠痛行为反应变化以及电针对海马神经型一氧化氮合酶(nNOS)、内皮型一氧化氮合酶(iNOS)、细胞内蛋白激酶G(PKG)基因表达的影响,分析针刺治疗慢性神经病理性疼痛的机制。方法:Wistar大鼠随机分为正常组、模型组、电针2Hz组、电针2Hz/15Hz组、电针100Hz组,每组8只。用手术线结扎坐骨神经造成病理性神经痛模型。电针双侧"足三里"-"阳陵泉",每次30min,每天1次,共2周。分别测定足底机械痛阈和热痛阈的变化(双侧缩腿潜伏期差值,PWLD)。用荧光定量RT-PCR法检测海马组织nNOS、iNOS、PKG基因的表达。结果:与正常组比,术后大鼠足底部热痛阈和机械痛阈明显降低(P<0.05);电针2 Hz组、2 Hz/15 Hz组、100 Hz组动物的痛阈显著升高(P<0.05);3个电针组之间PWLD值差异虽无统计学意义(P>0.05),但2Hz组、2Hz/15Hz组电针后3～10d的PWLD的降低稍优于100Hz组。与正常组比,模型组海马nNOS、PKG基因的表达量均升高或明显升高(P<0.05),iNOS的表达量则没有明显变化(P>0.05)。与模型组比,3个电针组nNOS、PKG基因表达量均显著降低(P<0.05),但3组间差异无统计学意义(P>0.05)。结论:电针"足三里"-"阳陵泉"穴区能明显升高CCI大鼠的痛阈,该作用可能与其下调海马nNOS、PKG基因表达水平有关。

Objective To observe the effect of etectroacupuncture （EA） at ＂Zusanli＂（ST 36）-＂Yanglingquan＂（GB 34） on pain behavior and expression of hippocampal neuronal nitric oxide synthase （nNOS）, inducible nitric oxide synthase（iNOS）and cGMP-dependent protein kinase （PKG） mRNA in rats with chronic neuropathic pain so as to analyze its mechanism underlying an- algesia. Methods Forty male Wistar rats were randomly divided into control, CO1 model, EA-2 Hz, EA-2 Hz/15 Hz, EA-100 Hz groups, with 8 cases in each group. Chronic neuropathic pain model was established by ligature of the left sciatic nerve under an- esthesia （Urethane ＋ Alpha-Ohloralose） except rats in the control group. EA{2 Hz, 2 Hz/15 Hz, 100 Hz, 1 mA） was applied to bi- lateral ＂Zusanii＂（ST 36）-＂Yanglingquan＂（GB 34） for 30 rain, once each day for 2 weeks. The thermal and mechanical paw with- drawal latencies （pain thresholds） of the bilateral limbs were detected before and after EA interventions. The hippocampal tissue of the rat was collected for detecting the expression levels of nNOS, iNOS and PKG genes using quantitative real-time-PeR tech- nique. Results In comparison with the control group, the thermal and mechanical pain thresholds of the model group were de- creased obviously （P〈0.05）. Compared with the model group, both thermal and mechanical pain thresholds of the EA-2 Hz, EA- 2 Hz/15 Hz and EA-100 Hz groups were markedly increased after EA intervention for 3, 7, 10 and 14 days （P〈0. 05）. Compared with the controt group, the expression levels of hippocampal nNOS and PKG mRNA were significantly and moderately up-regulated in the model group （P〈0.05）. While in comparison with the model group, the expression levels of hippocampal nNOS and PKGmRNA in the EA-2 Hz, EA-2 Hz/15 Hz and EA-100 Hz groups were markedly down-regulated （P〈0.05）. No significant differences were found among the EA-2 Hz, EA-2 Hz/15 Hz and EA-100 Hz groups in the analgesic effect and in down-regulating hippocampal nNOS and PKG mRNA expression （P〉0.05）. However, the recovery state of the pain reaction of both EA-2 Hz and EA-2 Hz/ 15 Hz groups was relatively better than that of the EA-100 Hz group from day 3 to 10 after EA intervention. Cenclusion EA stimulation of ＂Zusanli＂（ST 36）-＂Yanglingquan＇（GB 34） at 2 Hz, 2 Hz/15 Hz and 100 Hz can significantly suppress chronic neuro- pathic pain induced in COl rats, which may be closely associated with its effects in down-regulating hippocampal nNOS and PKG mRNA expression levels.