Mechanism of early anoxia-induced suppression of the GABAA-mediated inhibitory postsynaptic current.
Mechanism of early anoxia-induced suppression of the GABAA-mediated inhibitory postsynaptic current.
复制标题
早期缺氧诱导抑制 GABAA 介导的抑制性突触后电流的机制。
DOI：
--
复制
发表时间：
1994
影响因子：
2.5
通讯作者：
N. Hershkowitz
中科院分区：
文献类型：
--
作者：
A. Katchman;S. Vicini;N. Hershkowitz
1.本研究探讨了缺氧抑制21 ~ 28日龄大鼠海马脑片CA 1区神经元γ-氨基丁酸-A（GABAA）介导的抑制性突触后电流（IPSCs）的机制。通过全细胞膜片钳记录检查细胞，并通过将切片从含氧人工脑脊液（ACSF）灌注到用95%N2 - 5%CO2饱和的ACSF来诱导缺氧。2.缺氧时以固定保持电位（VH = -60 mV）刺激Schaffer侧副连合投射诱发的突触反应显示，IPSC对缺氧引起的抑郁反应比兴奋性突触后电流更敏感。所有随后的研究通过在存在细胞外3-氨基丁酸的情况下直接刺激辐射层中的GABA中间神经元来单独检查GABA介导的IPSC突触反应。（2-羧基哌嗪-4-基）丙基-1-膦酸（CPP）（20 μ M）和6-氰基-7-硝基喹喔啉-2，3-二酮（CNQX）（50 μ M）以阻断GABA能电流和细胞内QX-314（利多卡因N-乙基溴，1 mM）以阻断GABA介导的电流。当以这种方式研究时（VH = -60 mV），GABAA介导的IPSC似乎在暴露于缺氧后从外向电流变为内向电流。3. GABAA介导的IPSC的电流-电压关系显示，这些变化是由于IPSC逆转电位的正移而导致的，而电导没有显著变化。因此，在膜片钳下，明显的IPSC抑制可能是由于细胞外氯离子浓度的降低。用含有高细胞内氯离子浓度的微量移液器观察到类似的结果。4.在河豚毒素（1 μ M）存在下，用含有高细胞内氯离子浓度的微量移液管检查微型自发IPSC。微型IPSCs（mIPSCs）表现为自发的瞬时内向电流。与缺氧诱导的细胞外氯化物减少一致，缺氧发作后mIPSC的平均振幅增加。在缺氧期间，上升和衰减时间也显着减少。mIPSC的频率也增加了约300%。5.通过测量由20-mV超极化脉冲产生的电流来检查细胞的静息输入电阻。缺氧后2分钟，观察到电阻显着降低。这种情况仍然发生，尽管程度较低，在存在多巴胺能阻断剂（20 μ M CPP加50 μ M CNQX）的情况下。在GABA能（印防己毒素，100 μ M）和谷氨酸能阻断剂的存在下，在缺氧2分钟后，静息输入电阻没有明显降低。（400字处截断摘要）
1. We investigated the mechanism of hypoxia-induced depression of gamma-aminobutyric acid-A (GABAA)-mediated inhibitory postsynaptic currents (IPSCs) in CA1 neurons of hippocampal slices from 21- to 28-day-old rats. Cells were examined by whole-cell patch-clamp recording and hypoxia was induced by switching perfusion of the slice from oxygenated artificial cerebral spinal fluid (ACSF) to ACSF saturated with 95% N2-5% CO2. 2. Synaptic responses evoked by stimulation of the Schaffer collateral-commissural projection at a fixed holding potential (VH = -60 mV) during anoxia revealed that the IPSC appeared more sensitive than the excitatory postsynaptic current to anoxia-induced depression. All subsequent studies examined the GABAA-mediated IPSC synaptic responses in isolation by direct stimulation of GABA interneurons in the stratum radiatum in the presence of extracellular 3-(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (CPP) (20 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (50 microM) to block glutamatergic currents and intracellular QX-314 (lidocaine N-ethyl bromide, 1 mM) to block GABAB-mediated currents. When studied in this manner (VH = -60 mV) the GABAA-mediated IPSC appeared to change from an outward to inward current after exposure to anoxia. 3. The current-voltage relationship of GABAA-mediated IPSCs revealed that these changes resulted from a positive shift in the IPSC reversal potential without a significant change in the conductance. Thus under patch clamp apparent IPSC inhibition may result from a decrease in the extracellular concentration of chloride ions. Similar findings were observed with micropipettes that contained high intracellular chloride concentrations. 4. Miniature spontaneous IPSCs were examined in the presence of tetrodotoxin (1 microM) with micropipettes containing high intracellular chloride concentrations. The miniature IPSCs (mIPSCs) appeared as spontaneous transient inward currents. Consistent with an anoxia-induced decrease in extracellular chloride, the mean amplitude of the mIPSCs increased after the onset of anoxia. A significant decrease in rise and decay time was also noted during anoxia. The frequency of the mIPSCs also increased by approximately 300%. 5. The resting input resistance of the cells was examined by measuring the current resulting from a 20-mV hyperpolarizing pulse. A significant reduction in resistance was observed 2 min after the onset of anoxia. This still occurred, although to a lesser degree, in the presence of glutamatergic blockers (20 microM CPP plus 50 microM CNQX). In the presence of both GABAergic (picrotoxin, 100 microM) and glutamatergic blockers no significant reduction in resting input resistance was apparent after 2 min of anoxia.(ABSTRACT TRUNCATED AT 400 WORDS)