缺氧对离体培养的海马神经元兴奋性的影响

Alterations of excitability from rat hippocampal neurons induced by various hypoxic duration

目的探讨不同缺氧处理时间对海马神经元兴奋性的影响。方法原代培养海马神经元经(95%N2/5%CO2)混合气饱和人工脑脊液(artificial cerebrospinal fluid,ACSF)灌流缺氧,选取灌流10、15、20、25、30、35、404、5 min后8个时段,采用全细胞记录模式测定神经细胞膜电位;电流钳下跃阶电流(+60 pA^+40 pA,step=10 pA,时长200 ms)刺激,测定神经细胞阈强度。对照组神经元灌流(95%O2/5%CO2)混合气饱和ACSF。结果缺氧处理15、20 min后神经细胞膜电位数值升高,较对照组差异有统计学意义(P<0.05);而缺氧处理30、35、404、5 min后神经细胞膜电位数值低于对照组膜电位(P<0.05)。神经细胞缺氧处理152、0 min后,其阈强度高于对照组(P<0.05);而缺氧处理30、35、40、45 min后神经细胞阈强度低于对照组(P<0.05)。结论缺氧早期神经细胞膜电位呈现超极化,阈强度增高,兴奋性降低;随缺氧程度加剧,神经细胞膜电位呈现去极化,阈强度减低,兴奋性增高。

Objective To explore alterations of excitability from hippocampal neurons subjected to hypoxia in various duration.Methods Hypoxia episodes（10,15,20,25,30,35,40,45 min duration）of primary cultured hippocampal neurons were produced by switching from ACSF equilibrated with 95% O2/ 5% CO2 to ACSF equilibrated with 95% N2 / 5% CO2.Membrane potentials of neurons in the different hypoxia duration were measured by whole-cell recording,and then threshold intensity,that was minimum current intensity inducing action potential in neuron,was tested by step currents（-60 pA～＋40 pA,step=10 pA,time=200 ms）in neurons exposed to various hypoxia duration.Neurons in control group were perfused with ACSF equilibrated with 95% O2/5%CO2.Results Membrane potential values of hippocampal neurons with exposure to hypoxia for 15,20 min were higher than those in control group（P0.05）;and as compared with control group,membrane potential values of hippocampal neurons with exposure to hypoxia for 30,35,40,45 min were decreased（P0.05）.Threshold intensities of neurons subjected to hypoxia for 15,20 min were higher than those in control group（P0.05）,however,threshold intensities of neurons with exposure to hypoxia for 30,35,40,45 min were lower than those in control group（P0.05）.Conclusion Hippocampal neurons take on hyperpolarization of membrane potential,enhancement of threshold intensity,and thereby decrease of excitability in early hypoxic stage.With hypoxic time extension,hippocampal neurons present depolarization of membrane potential,reduction of threshold intensity,and so increase of excitability.