不同浓度七氟醚对老年大鼠海马神经发生和恐惧记忆的影响

Effect of different concentrations of sevoflurane on the neurogenesis and fear memory in the hippocampus of senile rats

目的探讨七氟醚对老年大鼠海马神经发生和恐惧记忆的影响。方法 SPF级健康雄性SD大鼠24只,20月龄,体重250~300g,采用随机数字表法分为三组:对照组(C组)、3%七氟醚组(LS组)和4%七氟醚组(HS组),每组8只。C组吸入空-氧混合气体,LS组予3%七氟醚吸入,HS组予4%七氟醚吸入,吸入时间均为3h。吸毕24h进行条件恐惧实验(场景和声音)检测大鼠恐惧记忆。先进行声音和电流刺激训练,训练后2h和24h进行场景和声音实验。行为学实验结束后立即处死大鼠,采集脑组织进行免疫荧光分析海马中Ki67、NeuN、GFAP阳性细胞数和形态学变化。结果与C组比较,HS组和LS组大鼠24h场景实验僵直时间明显缩短,海马齿状回中Ki67、NeuN、GFAP阳性细胞数明显减少(P<0.05)。与HS组比较,LS组大鼠24h场景实验僵直时间明显延长,齿状回中Ki67、NeuN、GFAP阳性细胞数明显增多(P<0.05)。C组大鼠海马齿状回组织结构完整、清晰,细胞排列整齐有序,LS组和HS组大鼠的海马齿状回均出现细胞排列紊乱,结构完整性破坏,且HS组破坏更为严重。结论 3%和4%七氟醚吸入3h均能抑制老年大鼠海马神经发生,引起恐惧记忆下降。4%七氟醚对海马神经发生和恐惧记忆的损伤更重。

Objective To investigate the effect of sevoflurane on hippocampal neurogenesis and fear memory of senile rats.Methods Twenty-four SPF healthy male Sprague-Dawley（SD）rats aged20 months and weighing 250-300 g were randomly divided into three groups：control group（group C）,3% sevoflurane group（group LS）and 4% sevoflurane group（groupHS）,n=8 for each group.The rats in group C inhaled air-oxygen mixed gas.The rats in group LS or HS inhaled 3% or 4%sevoflurane for 3 h,respectively.At time point of 24 hafter inhalation,condition fear test（scene test and sound test）was used to detect the fear memory of rats.Rats were sacrificed immediately after behavioral experiments,and brain tissues were collected for immunofluorescence analysis of Ki67,NeuN,GFAP-positive cells and morphological changes in the hippocampus.Results Compared with group C,freezing time at 24 hin the context test decreased,and the number of Ki67,NeuN and GFAP-positive cells in hippocampal dentate gyrus decreased in rats of groupHS and LS（P〈0.05）.Compared with groupHS,freezing time at 24 hin the context test increased,and the number of Ki67,NeuN and GFAP-positive cells in the dentate gyrus increased in rats of group LS（P〈0.05）.The dentate gyrus in the hippocampus of rats in group C had intact and clear tissue structure,and the cells were arranged neatly and orderly.In the dentate gyrus of rats in group LS and groupHS,the arrangement of cells was chaotic and the structural integrity was destroyed,and the destruction of groupHS was more severe.Conclusion 3% and 4% sevoflurane inhalation inhibit the hippocampal neurogenesis and induce decline of fear memory in senile rats.The effects of 4% sevoflurane is more severe than 3% sevoflurane.