右美托咪定减轻七氟烷诱发幼鼠中枢神经毒性作用与NKCC1/KCC2的关系

Relationship between dexmedetomidine-induced reduction of sevoflurane-induced neurotoxicity and NKCC1/KCC2 in neonatal rats

目的评价右美托咪定减轻七氟烷诱发幼鼠中枢神经毒性作用与钠离子-钾离子-氯离子共转运体1(NKCC1)/钾离子-氯离子共转运体2(KCC2)的关系。方法健康雄性SD大鼠80只,7日龄,采用随机数字表法分为4组(n=20):对照组(C组)、七氟烷麻醉组(S组)、右美托咪定对照组(D组)、七氟烷+右美托咪定组(SD组)。S组置于2.5%七氟烷培养箱6 h构建七氟烷麻醉模型。SD组腹腔注射右美托咪定1.0μg/kg,随后行七氟烷麻醉。于麻醉结束后24 h时,采用Western blot法检测海马cleaved caspase-3、NKCC1和KCC2的表达水平;于麻醉结束后35 d时,采用Y迷宫实验检测认知功能,采用尼式染色法进行海马CA1区神经元计数。结果与C组比较,S组和SD组新异臂停留时间百分比和海马CA1区神经元计数降低,海马cleaved casepase-3和NKCC1表达上调,KCC2表达下调,NKCC1/KCC2比值升高(P<0.05),D组上述指标差异无统计学意义(P>0.05);与S组比较,SD组新异臂停留时间百分比和海马CA1区神经元计数升高,海马cleaved casepase-3和NKCC1表达下调,KCC2表达上调,NKCC1/KCC2比值降低(P<0.05)。结论右美托咪定减轻七氟烷诱发幼鼠中枢神经毒性的机制可能与维持NKCC1/KCC2表达相对稳定有关。

Objective To evaluate the relationship between dexmedetomidine-induced reduction of sevoflurane-induced neurotoxicity and cation-chloride cotransporters Na+-K+-2Cl--1(NKCC1)/K+-2Cl--2(KCC2)in neonatal rats.Methods Eighty healthy male Sprague-Dawley rats at postnatal day 7 were divided into 4 groups(n=20 each)using a random number table method:control group(group C),sevoflurane anesthesia group(group S),dexmedetomidine group(group D),and sevoflurane and dexmedetomidine group(group SD).Rats were exposed to 2.5%sevoflurane for 6 h to establish the model of sevoflurane anesthesia in group S.Dexmedetomidine 1.0μg/kg was intraperitoneally injected,and then sevoflurane anesthesia was performed in group SD.The expression of cleaved caspase-3,NKCC1 and KCC2 was detected by Western blot at 24 h after the end of anesthesia.At 35 days after the end of anesthesia,the cognitive function was assessed using the Y maze test,and the neurons in the hippocampal CA1 area were counted using the Nissan staining method.Results Compared with group C,the percentage of time spent in novel arm and the number of neurons in hippocampal CA1 area were significantly decreased,the expression of cleaved caspase-3 and NKCC1 was up-regulated,the expression of KCC2 was down-regulated,and the ratio of NKCC1/KCC2 was increased in S and SD groups(P<0.05),and no change was found in the above indicators in group D(P>0.05).Compared with group S,the percentage of time spent in novel arm and the number of neurons in hippocampal CA1 area were significantly increased,the expression of cleaved caspase-3 and NKCC1 was down-regulated,the expression of KCC2 was up-regulated,and the ratio of NKCC1/KCC2 was decreased in group SD(P<0.05).Conclusion The mechanism of dexmedetomidine attenuating sevoflurane-induced neurotoxicity may be related to maintaining the relatively stable expression of NKCC1/KCC2 in neonatal rats.