右美托咪定对布比卡因脊髓神经毒性的作用及相关机制

Effects of dexmedetomidine on neurotoxicity of bupivacaine in spinal cord and related mechanisms

目的:探讨右美托咪定是否通过激活Pi3k/Akt通路抑制神经元凋亡,从而减轻布比卡因脊髓神经毒性。方法:选择24只SPF级SD大鼠,随机分成3组:生理盐水组(S组)、布比卡因组(B组)、右美托咪定预处理组(D组)。SD大鼠进行鞘内置管后分别进行以下处理:S组鞘内注射0.12μL/g生理盐水,连续3次每次间隔90 min,B组鞘内注射0.12μL/g的5%的布比卡因,连续3次每次间隔90 min,D组腹腔注射50μg/kg的右美托咪定,30 min后连续3次鞘内注射5%布比卡因每次间隔90min。各组于给药后0 d、1 d、2 d、3 d测大鼠甩尾反应潜伏期(TFL),0 d是在鞘内注射生理盐水或者布比卡因后的90 min进行甩尾测试和运动功能评分,换算成最大抗辐射效应百分比(%MPE)以进行感觉功能的评估,并行运动功能(BBB)评分。给药后3 d取材,取腰膨大处脊髓组织。HE染色光镜下观察脊髓组织损伤情况,Western blotting法检测各组Cleaved-caspase3、Bax、Bcl-2、Pi3k、p-Pi3k、Akt、P-Akt蛋白量表达情况,免疫荧光法检测神经元中Bax和Bcl-2表达情况。结果:与S组相比,B组和D组%MPE评分增高;BBB评分下降;HE染色光镜下脊髓损伤严重;Cleaved-caspase3和Bax蛋白表达量升高,Bcl-2、pPi3k、p-Akt表达下降(均P<0.05)。与B组相较,D组%MPE评分下降,脊髓组织损伤程度较轻,Bax蛋白表达量下降,Bcl-2、pPi3k、p-Akt表达量上升(P<0.05)。结论:右美托咪定抑制脊髓神经元凋亡从而减轻布比卡因脊髓神经毒性,其机制可能与激活Pi3k/Akt通路有关。

Objective:To investigate whether dexmedetomidine inhibits neuronal apoptosis through activation of Pi3k/Akt pathway and thereby reduces the neurotoxicity of bupivacaine in spinal cord.Methods:Twenty-four SPF SD rats were randomly divided into three groups:saline group(S group),bupivacaine group(B group),and dexmedetomidine pretreatment group(D group).After intrathecal catheterization,the following treatments were performed:group S was injected intrathecally with 0.12μL/g saline for three consecutive times at 90 min intervals,group B was injected intrathecally with 0.12μL/g 5%bupivacaine for three consecutive times at 90 min intervals,and group D was injected intraperitoneally with 50μg/kg dexmedetomidine followed by three consecutive intrathecal injections of 5%bupivacaine at 90 min intervals 30 minutes later.After modelling,the tail-flick latency(TFL)was measured at 0 d,1 d,2 d and 3 d in each group.For 0 d,tail-flick test and motor function evaluation were conducted 90 min after intrathecal injection of saline or bupivacaine and converted into percentage of maximum possible effect(%MPE)for the assessment of sensory function,and BBB scores were measured for motor function.The spinal cord tissues in the lumbar enlargement region were collected 3 d after drug administration.Spinal cord tissue damage was observed using HE-staining microscopy,the expressions of Cleaved-cas-pase3,Bax,Bcl-2,Pi3k,p-Pi3k,Akt,P-Akt protein in each group were detected by Western blotting,and Bax and Bcl-2 expression in neurons were detected by immunofluorescence.Results:Compared with groupS,groups B and D had increased%MPE scores,decreased BBB scores,severe spinal cord tissue damage under HE-staining microscopy,increased expression of Cleaved-caspase3 and Bax protein,and decreased expression of Bcl-2,p-Pi3k,and p-Akt(all P<0.05).Compared with group B,group D had decreased%MPE scores,less spinal cord tissue damage,decreased Bax protein expression,and increased Bcl-2,p-Pi3k,and p-Akt expression(P<0.05).Conclusion:Dexmedetomidine inhibits spinal cord neuronal apoptosis and thus attenuates the neurotoxicity of bupivacaine in spinal cord.Its mechanism may be related to the activation of Pi3k/Akt pathway.