地佐辛对大鼠坐骨神经干动作电位的影响

Effect of Dezocine on the action potential of sciatic nerve stem of rats

目的应用电生理学方法观察地佐辛（Dezocine，DZ）对大鼠离体坐骨神经干动作电位阈强度、最适强度、幅值及传导速度的影响，为探讨地佐辛对外周神经系统的作用及其机制提供理论依据。方法将制备好的大鼠坐骨神经干置于生理盐水中浸泡10min，分别测定其神经干动作电位的阈强度、最适强度、幅值和传导速度；再将其随机分为5个实验组（n=8），分别为地佐辛0．25mg／ml、2．5mg/ml和5．0mg／ml孵育组、0．25％利多卡因孵育组、5mg／ml地佐辛＋0．25％利多卡因混合孵育组，孵育20min后分别测定其上述指标的变化；经5．0mg／ml地佐辛孵育后的坐骨神经干再分为3组，置于3种不同浓度（0．02mg/ml、0．2mg／ml、0．4mg／ml）的盐酸纳洛酮溶液（Naloxone，Nal）中孵育20min后，观察其上述指标的变化。结果与地佐辛孵育前（生理盐水孵育）相比，0．25mg／ml的地佐辛处理后坐骨神经干的动作电位阈强度、最适强度、幅值和传导速度的改变差异无统计学意义（P〉0．05）；而2．5mg/ml、5．0mg/ml地佐辛处理坐骨神经干后，动作电位的阈强度P〈0．01）和最适强度显著升高（P〈0．01），幅值显著降低（P〈0．01），动作电位的传导速度显著减慢（P〈0．05，P〈0．01）。与盐酸纳洛酮处理前（地佐辛处理后）相比，0．02mg／ml盐酸纳洛酮处理后坐骨神经干的动作电位阈强度、最适强度、幅值和传导速度的改变差异无统计学意义（P〉0．05）；0．2mg／ml和0．4mg／ml盐酸纳济酮处理后的坐骨神经干动作电位的阈强度、最适强度显著降低（P〈0．05，P〈0．01），幅值和传导速度显著提高（P〈0．05，P〈0．01）。与单纯0．25％利多卡因孵育组相比，5．0mg／ml地佐辛＋0．25％利多卡因混合孵育组的动作电位较早消失。结论地佐辛能降低大鼠坐骨神经干的兴奋性，减慢坐骨神经动作电位的传导，盐酸纳洛酮抑制地佐辛引起的动作电位兴奋性的降低和传导速度的减慢；地佐辛能加速利多卡因的起效时间。

Objective The electrophysiological techniques were applied to investigate the effect of dezocine on the threshold intensity, the optimal intensity, and the conduction velocity of compound action potential of sciatic nerve stem of rats. It may provide a potential theoretical basis for the mechanism of dezocine action on the peripheral nerve system. Methods After incubating with normal saline for 10 rain, the sciatic nerve stems of rats were divided into five groups （0.25 mg/ml, 2.5 mg/ml, and 5.0 mg/ml dezocine, 0.25% lidocaine group, 5.0 mg/ml dezocine ＋ 0.25% lidocaine group）. Before and after the treatment for 20 min, the threshold intensity, the optimal intensity, and the conduction velocity of compound action potential of sciatic nerve stems were examined by BL-420 ＋ biological function experimental signal analysis system. There after, 5.0 mg/ml dezocine-treated sciatic nerve stems were then incubated in three different concentration ofnaloxone （0.02 mg/ml, 0.2 mg/ml, or 0.4 mg/ml） for 20min, thus to observe the alteration of threshold intensity, optimal intensity, and conduction velocity of compound action potential. Results Compared with the control group, dezocine treatment at dosage of 2.5 mg/ml and 5.0 mg/ml, but not 0.25 mg/ml obviously induced upregulation of threshold intensity and optimal intensity of compound action potential, and downregulation of the amplitude and conduction velocity of compound action potential of sciatic nerve stems （P〈0.05）. Naloxone treatment at dosage of 0.2 mg/ml and 0.4 mg/ml, but not 0.02 mg/ml significantly attenuated the increase of threshold intensity and optimal intensity of compound action potential, and the decrease of amplitude and conduction velocity of compound action potential induced by dezocine application. Compared with 0.25% lidocaine treatment group, 5.0 mg/ml dezocine and 0.25% lidocaine treatment showed cooperative effect on inhibiting the action potential of sciatic nerve stem. Conclusions Dezocine treatment significantly reduced the excitability and the conduction velocity of compound action potential of sciatic nerve stem in vitro, which can be rescued by naloxone application. Moreover, dezocine treatment also obviously accelerates the effectiveness of lidocaine.