七氟烷对不同性别新生大鼠认知功能影响的差异分析

Sex-specific effects of sevoflurane on cognitive function of postnatal rats

目的探讨七氟烷对不同性别新生大鼠认知功能影响的差异。方法82只出生后7 d(P7)SD大鼠,随机分为对照组与七氟烷处理组,然后按照性别分为以下亚组:雌性对照组、雄性对照组、雌性七氟烷处理组、雄性七氟烷处理组,每组19~22只。各组大鼠分别吸入空气或4%七氟烷4 h后,应用ELISA法检测外周血血清皮质酮、雌二醇(E2)水平,采用免疫组化法检测海马Ki-67和神经元核心抗原(NeuN)的表达。各组大鼠于P21行旷场实验,P35行Morris水迷宫实验。结果ELISA检测结果显示,与对照组相比,七氟烷处理组大鼠外周血血清皮质酮水平明显升高[(7.93±1.58)ng/ml vs.(11.60±1.41)ng/ml,P<0.05],E2水平差异无统计学意义[(35.0±8.25)pmol/L vs.(34.2±9.73)pmol/L,P>0.05];不同性别各亚组间皮质酮、E2水平差异无统计学意义(P>0.05)。免疫组化检测结果显示,与对照组相比,七氟烷处理组大鼠海马CA1区和齿状回区Ki-67、NeuN阳性细胞数均明显减少(P<0.05);不同性别各亚组大鼠海马CA1区和齿状回区Ki-67、NeuN阳性细胞数差异无统计学意义(P>0.05)。Morris水迷宫实验结果显示,获得性训练第4、5天,与雄性对照组相比,雄性七氟烷处理组大鼠平台潜伏期和移动距离均明显延长(P<0.01或P<0.05),雌性对照组与雌性七氟烷处理组大鼠平台潜伏期、移动距离差异无统计学意义(P>0.05);对位训练第2天,与雄性对照组相比,雄性七氟烷处理组大鼠平台潜伏期和移动距离明显延长(P<0.05),雌性对照组与雌性七氟烷处理组大鼠平台潜伏期、移动距离差异无统计学意义(P>0.05);对位探查训练中,各处理组及不同性别大鼠游泳速度、目标象限次数比较,差异均无统计学意义(P>0.05),但与雄性对照组相比,雄性七氟烷处理组大鼠平台潜伏期明显延长(P<0.01),目标象限耗时明显缩短(P=0.031)。结论七氟烷处理对新生大鼠血清皮质酮水平影响较大,可抑制海马神经干细胞增殖及神经元发生,成年后雄性大鼠学习能力有所减退,但对雌性大鼠无明显影响。

Objective To investigate the gender difference of cognitive function in neonatal rats treated with sevoflurane.Methods Eighty two postnatal 7-day(P7)SD rats were randomly divided into control group and sevoflurane treated group,then divided into the following subgroups according to gender:female control group,male control group,female sevoflurane treated group,and male sevoflurane treated group.After inhaling air or 4%sevoflurane for 4 hours,the levels of serum cortisone and estradiol(E2)were detected by ELISA,and the expressions of Ki-67 and neuronal core antigen(NeuN)in hippocampus were detected by immunohistochemistry.The open field experiment was performed with rat P21 and Morris water maze experiment was performed with rat P35 to explore the effects of sevoflurane exposure on the spatial cognitive function in different gender of rats.Results ELISA reveled that,compared with the control group,the serum cortisone level in sevoflurane treated group was significantly higher[(11.60±1.41)ng/ml vs.(7.93±1.58)ng/ml,P<0.05],while the serum E2 level showed no significantly different[(35.0±8.25)pmol/L vs.(34.2±9.73)pmol/L,P>0.05];and no significant difference existed in the levels of cortisone and E2 between different genders(P>0.05).Immunohistochemistry showed that the number of Ki-67 and NeuN positive cells in hippocampal CA1 and dentate gyrus(DG)decreased significantly in sevoflurane treated group than those in control group(P<0.05).Also,no significant difference existed in the expression of hippocampal neurons between different genders(P>0.05).Morris water maze test showed that no significant difference was found among female rats(P>0.05);compared with male control group,the platform latency and moving distance of male sevoflurane treated group were significantly prolonged at the forth and fifth day of acquired training(P<0.01 or P<0.05).At the second day of counterpoint training,the platform latency and movement distance of rats in male sevoflurane treated group were significantly prolonged(P<0.05).In counterpoint exploration training,the platform latency of rats in male sevoflurane treated group was significantly prolonged(P<0.01),and the time spent in the target quadrant reduced significantly(P=0.031).Conclusions Sevoflurane treatment has a great influence on the serum cortisone level of postnatal rats,may inhibit the proliferation of hippocampal neural stem cells and neurogenesis.The learning ability of male rats decreased after adulthood,but no obvious effect on female rats.