不同浓度罗哌卡因对幼兔脊髓和脊神经的毒性作用

Neurotoxic effects of ropivacaine on spinal cord and spinal nerves in young rabbits

目的探讨不同浓度罗哌卡因对幼兔脊髓和脊神经的毒性作用。方法日本大耳自幼兔120只，随机分为5组（n=24）：0．9％生理盐水阴性对照组（S组）、2％丁卡因阳性对照组（T组）和0．25％、0．5％、0．75％罗哌卡因组（R1-3组）。行L0.7穿刺后，各组于20s内鞘内注入生理盐水、2％丁卡因或不同浓度罗哌卡因各0．2ml。分别于鞘内给药后3、6h、7d时各取8只动物，行运动阻滞程度评估后处死，其中6只动物切取L5。段脊髓，HE染色后光镜下观察脊髓病理学结果；TUNEL法检测细胞凋亡情况，计算细胞凋亡指数（AI）；免疫组化法测定Bax蛋白和Bcl-2蛋白的表达水平。另2只动物切取L5.6段脊髓后角组织及神经根，透射电镜下观察脊髓和脊神经超微结构。结果凡组可见神经胶质细胞核轻度固缩，T组脊髓出现典型凋亡细胞，其余各组脊髓和脊神经超微结构基本正常。与T组比较，R1-3组运动阻滞显效时间延长（P〈0．05）；与R1组比较，R2.3组运动阻滞显效时间缩短（P〈0．05）。R1-3组与S组AI、Bax蛋白和Bcl-2蛋白表达水平差异无统计学意义（P〉0.05）；与T组比较，其余各组AI降低，Bax蛋白和Bcl-2蛋白表达下调（P〈0．05）。结论0．25％～0．75％罗哌卡因对幼兔脊髓和脊神经无毒性作用；Bax蛋白和Bcl-2蛋白表达上调可能参与了脊髓和脊神经毒性作用的发生。

Objective To investigate the neurotoxic effects of different concentrations of ropivacaine administered intrathecally（IT） on the spinal cord and spinal nerves in young rabbits and the possible mechanism. Methods One hundred and twenty 45 day old Japanese white rabbits of either sex weighing 1.0-1.5 kg were randomly divided into 5 groups （ n = 24 each） ： group I control; group Ⅱ 2% tetracaine; group Ⅲ , Ⅳ, Ⅴ0.25 % , 0.5 % , 0.75 % ropivacaine. The animals received 0.2 ml of normal saline （ in control group）, 2 % tetracaine （in groupⅡ ） or 0.25% , 0.5%, 0.75% ropivacaine （in group Ⅲ,Ⅳ,Ⅴ ） injected Ⅱ at L5.6 interspace over 20 seconds. The degree of motor block was assessed using Malinovsky scoring system （0 = normal movement, 3 = completely paralyzed） and the onset time of motor block was recorded. Eight animals each were killed at 3 h, 6 h and 7 d after IT injection. The lumbar segment （ L5.6 ） of spinal cord was immediately removed for histologic examination with electron microscope（2 animals）, detection of neuronal apoptosis （by TUNEL） and determination of Bax and Bcl-2 expression （by immuno-histochemistry）（ the other 6 animals）. Results The animals developed different degrees of motor block in the hindlegs in the 3 ropivacaine groups. The onset time became shorter with increasing concentration of ropivacaine. Electron microscopy showed that there was slight degree of nuclear shrinkage in tetracaine group. Typical apoptotic cells were also detected in the spinal cord in tetracaine group. The apoptosis index and the optical density of the cells expressing Bax or Bcl-2 were significantly lower in the control and 3 ropicacaine groups than in tetracaine group （P 〈 0.05 ）. Conclusions The concenlxation of ropivacaine 0.25 %- 0.75 % may notbe injurious to the spinal cord and spinal nerves in young rabbits. The upregulation of Bax and Bcl-2 expression may be involved in the initiation and development of neurotoxicity.