米诺环素对七氟烷麻醉致老龄小鼠认知障碍的改善作用及其机制

The improvement of minocycline on cognitive dysfunction induced by sevoflurane anesthesia in aged mice and its mechanism

目的探讨米诺环素对七氟烷麻醉诱导老龄小鼠认知障碍的改善作用及其机制。方法清洁级C57BL/6小鼠75只按照随机数字表法分为对照组(Con组)、七氟烷组(Sev组)、七氟烷+米诺环素组(Sev+Min组),每组25只。Sev组小鼠给予连续3 d,每天2 h的3%七氟烷麻醉;Sev+Min组小鼠先腹腔注射米诺环素(50 mg/kg),然后进行3%七氟烷麻醉,连续3 d,每天2 h;Con组小鼠腹腔注射50 mg/kg的生理盐水,1次/d,连续3 d。Morris水迷宫实验检测小鼠记忆功能。免疫组化观察小鼠BrdU标记的新生神经细胞。利用电生理技术检测小鼠离体脑片海马齿状回(dentate gyrus,DG)区的场兴奋性突触后电位(field excitatory postsynaptic potential,fEPSP)斜率变化。采用SPSS 21.0软件进行重复测量方差分析和SNK检验。结果定位航行实验显示,组别×时间交互作用明显(F=15.65,P<0.01)。空间探索结果显示,首次麻醉后第6天,与Con组比较,Sev组小鼠的逃避潜伏期明显增加(q=4.35,P<0.05),目标象限百分比(q=6.15,P<0.05)和进入原平台总次数(q=6.45,P<0.05)明显减少。与Sev组相比,Sev+Min组逃避潜伏期明显减少(q=3.01,P<0.05),目标象限百分比(q=3.21,P<0.05)和进入原平台总次数(q=3.48,P<0.05)明显增加。免疫组化结果显示,与Con组[(355.87±62.58)个]比较,Sev组小鼠BrdU阳性细胞数明显减少[(227.45±43.25)个,q=8.67,P<0.01]。与Sev组相比,Sev+Min组小鼠BrdU阳性细胞数[(338.73±47.27)个]增加,差异有统计学意义(q=8.68,P<0.01)。电生理结果显示,与Con组[(214.38±43.42)%]比较,Sev组小鼠的fEPSP斜率明显降低[(126.83±25.67)%,q=6.18,P<0.01)]。与Sev组相比,Sev+Min组的fEPSP斜率明显升高[(178.49±32.67)%,q=3.64,P<0.05]。结论七氟烷麻醉可导致老龄小鼠短期记忆功能损害,其机制与抑制神经细胞增殖和突触可塑性有关,而米诺环素可以缓解由七氟烷麻醉引起的认知损伤。

Objective To explore the improvement and its mechanism of minocycline on sevoflurane anesthesia induced cognitive dysfunction in aged mice.Methods Totally 75 aged clean-grade C57BL/6 mice were randomly divided into control(Con)group(n=25),sevoflurane(Sev)group(n=25)and sevoflurane+minocycline(Sev+Min)group(n=25).Anesthetic injury was induced by 3%sevoflurane(2 h/d for 3 days)in Sev group.Minocycline(50 mg/kg)was injected intraperitoneally first,and then 3%sevoflurane(2 h/d for 3 days)anesthesia was performed in Sev+Min group.Saline alone was injected intraperitoneally(once a day for 3 days)in Con group.The spatial memory function was detected by Morris water maze experiments.BrdU was used to label new neuron and the proliferation was observed by immunohistochemistry.The field excitatory postsynaptic potential(fEPSP)slope was measured in hippocampal dentate gyrus(DG)region of isolated brain slices by electricphysiological technique.The data were analyzed by repeated measures analysis of variance and SNK-q test using SPSS 21.0 software.Results Results from positioning navigation experiment showed that the group×time interaction effect of mice was significant(F=15.65,P<0.01).On the 6th day after anesthesia,compared with Con group,the escape latency of the original platform in Sev group was significantly increased(q=4.35,P<0.05)in space exploration experiment,while the target quadrant time ratio(q=6.15,P<0.05))and the mean annulus crossings(q=6.45,P<0.05)were significantly decreased.Compared with Sev group,the escape latency in Sev+Min group was significantly decreased(q=3.01,P<0.05),while the target quadrant time ratio(q=3.21,P<0.05)and the mean annulus crossings(q=3.48,P<0.05)were significantly increased.In immunohistochemistry experiment,the number of BrdU positive cells in Sev group was significantly reduced((227.45±43.25),q=8.67,P<0.01)compared with Con group(355.87±62.58).Compared with Sev group,the number of BrdU positive cells in Sev+Min group was significantly increased((338.73±47.27),q=8.68,P<0.01).In electricphysiological test,the fEPSP slope after high frequency stimulation in Sev group((126.83±25.67)%,q=6.18,P<0.01))was significantly lower than that in Con group((214.38±43.42)%).In Sev+Min group,the fEPSP slope was significantly higher((178.49±32.67)%,q=3.64,P<0.05)than that in Sev group.Conclusion Sevoflurane anesthesia can induce the short-term cognitive dysfunction in aged mice,and its mechanism is related to inhibiting neuron proliferation and synaptic plasticity.Minocycline can alleviate the damage caused by sevoflurane.