γ-氨基丁酸A型受体在七氟醚致新生大鼠远期认知功能障碍中的作用

Role of gamma-aminobutyric acid type A receptor in the long-term cognitive dysfunction of neonatal rats induced by sevoflurane

目的探讨γ-氨基丁酸A型受体(GABAAR)在七氟醚致新生大鼠远期认知功能障碍中的作用。方法将36只6日龄雄性Sprague Dawley大鼠随机分为对照组、七氟醚组和荷包牡丹碱组,每组12只。对照组大鼠吸入体积分数30%O26 h,七氟醚组和荷包牡丹碱组大鼠吸入体积分数2.1%七氟醚和30%O26 h,荷包牡丹碱组大鼠在七氟醚吸入前30 min腹腔注射荷包牡丹碱0.5 mg·kg^-1。3组大鼠干预后8周进行水迷宫实验,水迷宫实验后1周处死大鼠取脑组织,采用高尔基染色法观察大鼠海马锥体神经元树突棘密度,采用实时荧光定量聚合酶链反应检测大鼠海马组织中脑源性神经营养因子(BDNF) mRNA表达,Western blot法检测大鼠海马组织中BDNF蛋白表达。结果水迷宫实验显示,第1~3天3组大鼠逃避潜伏期比较差异无统计学意义(P> 0.05);第4~5天,七氟醚组大鼠逃避潜伏期长于对照组,荷包牡丹碱组大鼠逃避潜伏期短于七氟醚组(P <0.05);七氟醚组大鼠目标象限停留时间短于对照组,荷包牡丹碱组大鼠目标象限停留时间长于七氟醚组(P <0.05)。七氟醚组大鼠海马组织中BDNF mRNA和蛋白的相对表达量低于对照组(P <0.05),荷包牡丹碱组大鼠海马组织中BDNF mRNA和蛋白的相对表达量高于七氟醚组(P <0.05)。对照组、七氟醚组和荷包牡丹碱组大鼠海马锥体神经元树突棘密度分别为35.10±4.57、26.90±6.26、32.40±4.92;七氟醚组大鼠海马锥体神经元树突棘密度小于对照组(P <0.05),荷包牡丹碱组大鼠海马锥体神经元树突棘密度大于七氟醚组(P <0.05)。结论七氟醚可导致新生大鼠远期认知功能障碍,GABAAR竞争性拮抗剂荷包牡丹碱可明显改善大鼠远期认知功能障碍,其机制可能与上调海马组织内BDNF表达及增强海马突触可塑性有关。

Objective To investigate the role of gamma-aminobutyric acid type A receptor(GABA AR)in the long-term cognitive dysfunction of neonatal rats induced by sevoflurane.Methods Thirty-six six days old male Sprague Dawley rats were randomly divided into control group,sevoflurane group and bicuculline group,with twelve rats in each group.The rats in the control group inhaled 30%O 2 for 6 hours,and the rats in the sevoflurane group and bicuculline group inhaled 2.1%sevoflurane and 30%O 2 for 6 hours.The rats in the bicuculline group were treated with bicuculline 0.5 mg·kg-1 by intraperitoneal injection at 30 minutes before sevoflurane inhalation.The rats in the three groups were tested by water maze after 8 weeks.One week after the water maze test,the rats were sacrificed to take brain tissues.The dendrite spine density of hippocampal pyramidal neuron was observed by Golgi staining,the expression of brain-derived neurotrophic factor(BDNF)mRNA in hippocampus was detected by real-time fluorescence quantitative polymerase chain reaction,and the expression of BDNF protein in hippocampus was detected by Western blot.Results Water maze test showed that there was no significant difference in escape latency of rats among the three groups on the 1 st to 3 rd day(P>0.05).On the 4 th and 5 th day,the escape latency of rats in the sevoflurane group was longer than that in the control group,and the escape latency of rats in the bicuculline group was shorter than that in the sevoflurane group(P<0.05).The target quadrant retention time of rats in the sevoflurane group was shorter than that in the control group,and the target quadrant retention time of rats in the bicuculline group was longer than that in the sevoflurane group(P<0.05).The relative expression of BDNF mRNA and protein in hippocampus of rats in the sevoflurane group was lower than that in the control group(P<0.05).The relative expression of BDNF mRNA and protein in hippocampus of rats in the bicuculline group was higher than that in the sevoflurane group(P<0.05).The dendrite spine density of hippocampal pyra midal neuron of rats in the control group,sevoflurane group and bicuculline group was 35.10±4.57,26.90±6.26 and 32.40±4.92,respectively.The dendrite spine density of hippocampal pyramidal neuron of rats in the sevoflurane group was less than that in the control group(P<0.05).The dendrite spine density of hippocampal pyramidal neuron of rats in the bicuculline group was higher than that in the sevoflurane group(P<0.05).Conclusion Sevoflurane can lead to long-term cognitive dysfunction of neonatal rats,the GABA AR competitive antagonist bicuculline can significantly improve the long-term cognitive dysfunction of rats,the mechanism may be related to the up-regulation of BDNF expression and the enhancement of synaptic plasticity in hippocampus.