右美托咪定辅助氯胺酮麻醉对大鼠海马区神经细胞的保护作用

Dexmedetomidine and ketamine combined with anesthesia play an neuroprotective role in hippocampus of rats

目的探讨右美托咪定辅助氯胺酮麻醉对大鼠海马区神经细胞的保护作用。方法将32只SD大鼠按照随机数字表法分为空白对照组、氯胺酮组、右美托咪定组和联合用药组,每组8只。空白对照组腹腔注射生理盐水50 m L/kg,间隔5 min皮下注射生理盐水50 m L/kg;氯胺酮组腹腔注射氯胺酮70 mg/kg,间隔5 min皮下注射生理盐水50 m L/kg;右美托咪定组腹腔注射右美托咪定25μg/kg,间隔5 min皮下注射生理盐水50 m L/kg;联合用药组腹腔注射氯胺酮70 mg/kg,间隔5 min皮下注射右美托咪定25μg/kg;各组均每天注射1次,连续注射3天。各组随机取4只,检测首次注射即刻(t0)及末次注射15、30、45、60、75、90 min(t1~t6)呼吸频率、翻正反射消失时间、翻正反射消失持续时间以及夹尾反射完全消失时间,Morris水迷宫实验检测各组训练1~5天的逃避潜伏期。各组剩余大鼠末次注射结束,断头处死,TUNEL法检测海马区神经细胞凋亡率,Western blotting法检测PKC、ERK1/2、Bcl-2蛋白表达。结果与联合用药组比较,氯胺酮组翻正反射消失时间明显延长,镇静维持时间、翻正反射消失持续时间明显缩短,两组比较P均<0.05。t1、t2、t3时,氯胺酮组呼吸频率均显著高于空白对照组、右美托咪定组和联合用药组同时间(P均<0.05)。空白对照组、右美托咪定组、联合用药组各时间逃避潜伏期比较P均>0.05;训练第4、5天,氯胺酮组逃避潜伏期较空白对照组、右美托咪定组和联合用药组明显延长(P均<0.05)。氯胺酮组神经细胞凋亡率明显高于空白对照组、右美托咪定组和联合用药组(P均<0.05),而空白对照组、右美托咪定组和联合用药组神经细胞凋亡率比较P均>0.05。氯胺酮组海马区PKC、ERK1/2、Bcl-2蛋白表达明显低于空白对照组、右美托咪定组和联合用药组(P均<0.05),而空白对照组、右美托咪定组和联合用药组海马区PKC、ERK1/2、Bcl-2蛋白表达比较P均>0.05。结论右美托咪定辅助氯胺酮麻醉对大鼠海马区神经细胞凋亡具有保护作用,其作用机制可能与激活PKC-ERK1/2-Bcl-2信号通路有关。

Objective To explore the protective effect of ketamine and dexmedetomidine combined with anesthesia on nerve cells in hippocampus of rats. Methods A total of 32 SD rats were randomly divided into the negative control group（ NC group）,ketamine（ K） group,dexmedetomidine（ D） group,and K ＋ D group with 8 rats in each group. In the NC group,50 m L/kg normal saline was injected intraperitoneally,and normal saline was injected subcutaneously after 5 min.In the ketamine group,70 mg/kg ketamine was injected intraperitoneally,and normal saline was injected subcutaneously after 5 min. In the dexmedetomidine group,50 m L/kg normal saline was injected intraperitoneally,and 25 μg/kg dexmedetomidine was injected subcutaneously after 5 min. In the K ＋ D group,70 mg/kg ketamine was injected intraperitoneally,and 25 μg/kg dexmedetomidine was injected subcutaneously after 5 min. The breathing rates,righting reflex time was recorded,the memory function of rats was measured by Morris water maze test at the moment of injection（ t0）,at the injection of 15,30,45,60,75,and 90 min（ t1-t6）. The rats were sacrificed after the administration,neuronal apoptosis in CA region was measured by TUNEL assay,and the expression of PKC,ERK1/2,and Bcl-2 protein was measured by Western blotting. Results Compared with the K ＋ D group,the righting reflex disappeared time of the ketamine group was significantly prolonged,the sedation duration and righting reflex disappeared time was significantly shorter,the difference between the two groups was statistically significant（ all P〈0. 05）. The breathing rates of the ketamine group were significantly higher than those of the NC group,dexmedetomidine group,and K ＋ D group at t1,t2,t3（ all P〈0. 05）. There was no significant difference between NC group,dexmedetomidine group and K ＋ D group in the escape latency of each period（ all P〈0. 05）. On the 4th and 5th days of training,the escape latency of the ketamine group was significantly longer than that of NC group,dexmedetomidine group and K ＋ D group（ all P〈0. 05）. The neuronal apoptosis ratio of the ketamine group was significantly higher than that of NC group,dexmedetomidine group and K ＋ D group（ all P〈0. 05）. The expression of p-PKC,p-ERK1/2,and Bcl-2 protein of the ketamine group was significantly lower than that of NC group,dexmedetomidine group and K ＋ D group（ all P〈0. 05）. Conclusion Dexmedetomidine and ketamine combined with anesthesia have the protective effect on nerve cells in hippocampus of rats by the activation of PKC-ERK1/2-Bcl-2 signaling pathway.