电针对神经病理性痛大鼠脊髓NO/cGMP信号转导通路的影响

目的 探讨电针对神经病理性痛大鼠脊髓一氧化氮/环鸟苷酸(NO/cGMP)信号转导通路的影响.方法 清洁级雄性SD大鼠48只,体重190～210 g,随机分为3组(n=16):假手术组(S组)仅分离坐骨神经,不结扎;神经病理性痛组(NP组)采用坐骨神经慢性压迫性损伤(CCI)法制备神经病理性痛模型;电针组(E组)于CCI后11～17 d时采用穴位神经刺激仪进行电针刺激,刺激大鼠术侧委中穴与环跳穴,刺激频率2 Hz,波宽0.6 ms,起始电流强度1 mA,每10 min递增1 mA,刺激时间30 min,1次/d.于CCI前(基础状态)、CCI后10、16 d时测定机械痛阈和热痛阈.CCI后10 d时痛阈低于基础痛阈的30%为模型制备成功.CCI后17 d时处死大鼠,取脊髓组织,采用分光光度法测定脊髓总一氧化氮合酶(tNOS)、诱导型一氧化氮合酶(iNOS)和神经元型一氧化氮合酶(nNOS)的活性,免疫组化法测定脊髓背角nNOS和iNOS的表达,采用硝酸还原酶法测定脊髓NO含量,采用放射免疫分析法测定脊髓cGMP含量.结果 与基础值比较,NP组和E组CCI后机械痛阈和热痛阈降低(P＜0.01);与CCI后10 d时比较,E组CCI后16 d时机械痛阈和热痛阈均升高(P＜0.01);与S组比较,NP组机械痛阈和热痛阈降低,脊髓tNOS、nNOS活性、NO和cGMP含量升高,nNOS表达上调,E组机械痛阈和热痛阈降低(P＜0.05或0.01),其余指标差异无统计学意义(P＞0.05);与NP组比较,E组机械痛阈和热痛阈升高,脊髓tNOS和nNOS活性、NO和cGMP含量降低,nNOS表达下调(P＜0.05或0.01).3组脊髓iNOS活性和表达比较差异无统计学意义(P＞0.05).结论 电针减轻大鼠神经病理性痛的机制与抑制脊髓NO/cGMP信号转导通路有关.

Effect of electro-acupuncture on NO-cGMP signal pathway in spinal cord in a rat model of neuropathic pain

Objective To investigate the effect of electro-acupuncture on the spinal nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signal pathway in a rat model of neuropathic pain (NP). Methods Forty-eight pathogen-free male SD rats weighing 190-210 g were randomly divided into 3 groups (n = 16 each):group Ⅰ sham operation (group S); group Ⅱ group NP and group Ⅲ electro-acupuncture + NP (group E). NP was induced by chronic constrictive injury (CCI). Right sciatic nerve was exposed and 4 loose ligatures were placed on the sciatic nerve at 1 mm intervals with 4-0 chromic catgut. In group E Huantiao and Weizhong points on the operated side were stimulated with electric stimulator (frequency 2 Hz, wave length 0.6 ms, starting at a voltage of 1mA and increasing by 1 mA every 10 min) for 30 min once a day at 11-17 d after CCI. Pain threshold to mechanical and thermal nociceptive stimuli was measured before (T0 , baseline) and at 10 and 16 d after CCI (T1, T2). The animals were sacrificed at 17 d after CCI and the lumbar segment (L4-6) was removed for determination of the activities of total NO synthase (tNOS), induced and neural NOS (iNOS, nNOS) (by spectrophotometry), NO content (by nitrate reductase method) and cGMP content (by immuno-histochemistry) in the spinal cord in 8 animals and the expression of iNOS and nNOS in the dorsal horn of the spinal cord (by immuno-histochemistry) in another 8 animals in each group. Results CCI significantly decreased the mechanical and thermal pain threshold at T1 and T2 as compared with the baseline at T0 in group NP and E. Hyperalgesia induced by CCI was significantly attenuated by electro-acupuncture at T2 in group E as compared with group NP.CCI significantly increased tNOS and nNOS activities, NO and cGMP content in the spinal cord and up-regulated nNOS expression in the spinal dorsal horn. Electro-acupuncture significantly attenuated the CCI-induced increases in tNOS and nNOS activities, NO and cGMP content in the spinal cord and nNOS expression in the spinal dorsal horn. There was no significant difference in the iNOS activity among the 3 groups. Conclusion NO-cGMP signal pathway in the spinal cord is involved in the acupuncture analgesia.