大鼠蛛网膜下腔内注入不同浓度罗哌卡因对其行为学和超微结构的影响

目的：观察大鼠蛛网膜下腔内间断注射不同浓度的罗哌卡因12 h对其神经行为学和脊髓超微结构的影响,以探讨罗哌卡因的神经毒性。方法：雄性SD大鼠30只采用改良Yaksh法蛛网膜下腔内置入microspinal导管至脊髓腰段后,随机分为5组（n=6）：N组（对照组）经microspinal导管注入0.9%氯化钠0.12 mL/kg,每间隔1.5 h 1次,共8次;A,B,C和D组4组注药方式和体积同N组,注入药物分别为0.25%,0.5%,0.75% 和1.0%罗哌卡因。注药前和第1 次注药后12 h测定双后肢热刺激回缩阈值 （poster paw withdrawal latency to heat stimulation,PWHL）、机械刺激回缩阈值（poster paw withdrawal latency to mechanical stimulation,PWML）,并进行运动功能 （motor function,MF ）评分。测定神经行为学的各项指标后处死大鼠,取脊髓腰膨大组织,透射电镜下观察其超微结构的改变。结果：A,B,C,D 4组注药后30 s内双后肢麻痹;10~60 min双后肢肌张力恢复,其中A组大鼠在注药后10,20 min的MF评分与B,C,D组相比,差异有统计学意义（P＜0.05）,即A组大鼠双后肢肌张力恢复最快;而B,C组大鼠在注药后20 min的MF评分与D组比较,有统计学差异（P＜0.05）即D组大鼠双后肢及张力恢复最慢,B和C组介于A和D组之间。实验组各组（A,B,C,D组）与对照（N）组比较,双后肢PWHL和PWML的最大效应百分比（percent maximum possible effect, %MPE）无统计学差异（P＞0.05）。电镜结果显示,N组和A组脊髓超微结构正常;B组线粒体、内质网轻度水肿;C组脊髓髓鞘纤维板层结构疏松,轴索肿胀,局灶变性;D组脊髓神经元细胞核膜皱缩,线粒体空泡样变,内质网肿胀严重,局灶性脱髓鞘改变。结论：大鼠蛛网膜下腔内间断注射0.5%,0.75%,1.0%罗哌卡因12 h可使其脊髓超微结构产生浓度依赖性的改变。

Behavioral and ultrastructural changes of intrathecal administered ropivacaine in spinal cord of rats

ObjectiveTo investigate the behavioral and ultrastructural changes of intrathecal administration of different concentrations of ropivacaine for 12 h. MethodsThirty male SD rats were randomly divided into 5 groups (6 rats in each group):group N (control), group A (ropivacaine 0.25%), group B (ropivacaine 0.5%), group C (ropivacaine 0.75%),and group D (ropivacaine 1.0%). A polyurethane microcatheter was inserted into the lumbar subarachnoid space 8 cm according to Yaksh’s intrathecal administration. The rats in group N received saline 0.12 mL/kg for 8 times at 1.5 h interval through the catheter, and the rats in the other groups received different concentrations of ropivacaine in the same way as in group N. The poster paw withdrawal latency to heat (PWHL) and mechanical stimulation (von Fray filament) (PWML) were measured the day before the intrathecal administration and 12 hours after the first intrathecal administration of ropivacaine. Motor function (MF) was measured after the last intrathecal administration. After the behavior test, the rats were sacrificed and the lumber segments of the spinal cord were immediately removed for electron microscopic examination.ResultsA total hind limb paralysis was seen at 30 seconds and intramuscular strain gradually came back 10~60 minutes after the intrathecal administration of ropivacaine in group A, B, C, and D, but not in group N. The recovery time of motor block of group A was the shortest (P＜0.05), that of group D was the longest,and that of group B and C was between group A and D. Intrathecal administration of different concentrations of ropivacaine did not affect the percent maximum possible effect (%MPE) of PWHL and PWML. Electron microscopic examination showed that the spinal cords were normal in group N and A, slight edema of mitochondria and endoplasmic reticulum (ER) in group B, loosened fibrous layers in medullary sheath, edema and local degeneration of neuraxis in group C,and shrinkage of nuclear membrane, serious edema of ER, vacuolus change of mitochondria and local demyelination in group D.Conclusion Ropivacaine (0.5%, 0.75%, and 1.0%) administered intrathecally for 12 hours causes different degrees of ultrastructural changes in the spinal cord depending on concentrations.