Neuron-Glia Interaction and Neural Network Function Involved in Ischemic Brain Damage.

1.用fura-2标记取自P7-14大鼠的新皮质切片。在O_2-葡萄糖剥夺过程中，锥体细胞[Ca^<2+>] _i被监测。Ⅱ/Ⅲ层神经元的[Ca^<2+>] _i显著高于Ⅳ、Ⅴ或Ⅵ层神经元。[Ca^<2+>] _i升高的层间差异主要由NMDA受体介导。GABA还可增加O_2-葡萄糖剥夺时[Ca^<2+>] _i。在Cl^-梯度降低后，GABA诱导NMDA受体通道介导的[Ca^<2+>] _i大幅增加。这表明缺血时正常Cl^-梯度的丧失可能是GABA能抑制作用减弱和/或逆转的基础。因此，如果在脑缺血期间发生Cl^-平衡电位的移动，GABA可能在兴奋性毒性中起加重作用。我们建立了一种用6-甲氧基-N-乙基喹啉碘（MEQ）测定脑片中[Cl^-] i的光学成像方法。取自P1的新皮质切片 关于我们 0-14用MEQ标记大鼠，在O_2-葡萄糖剥夺过程中监测单个神经元的[Cl^-] ^i。O_2-葡萄糖剥夺可使[Cl^-] _i先降低后显著升高。前者通过抑制Na^+，K^+-2Cl ^-共转运蛋白介导。用Fura-2.3-NPA不可逆地增加星形胶质细胞的[Ca ^<2+>] _i，但在神经元中显著增加[Ca ^<2+]_i，研究了3.3-NPA诱导的神经胶质细胞/神经元混合培养的[Ca ^<2 +>]_i瞬变。星形胶质细胞内[Ca^<2+>] i的增加主要是由Na^+-Ca^<2+>交换系统的反向操作所促进的，而在神经元内，则是由不同的机制所介导的。此外，3-NPA杀死9%的星形胶质细胞，而只有4%的神经元。星形胶质细胞死亡之前，细胞膜出现气泡，[Ca ^<2+>] i持续升高后，细胞内[Ca^<2 +>] i突然升高。结果表明，星形胶质细胞比神经元更容易受到3-NPA诱导的细胞Ca^<2+>超载和毒性的影响。提出了星形胶质细胞和神经元之间能量产生的差异代谢。少

1. Slices of neocortex taken from P7-14 rats were labeled with fura-2. The [Ca^<2+>] _i was monitored pyramidal cells during O_2-glucose deprivation. Neurons in layer II/III showed significantly greater increases in [Ca^<2+>] _i than those in layers IV, V, or VI.The laminar difference in terms of the [Ca^<2+>] _i increases was primarily mediated by NMDA receptors. GABA might also act to increase [Ca^<2+>] _i during O_2-glucose deprivation. After a reduction in the Cl^- gradient, GABA induced a large [Ca^<2+>] _i increase mediated by NMDA receptor-channels. This indicates that a loss of the normal Cl^- gradient during ischemia might underlie the reduction and/or reversal of the GABAergic inhibition. Thus GABA may play an aggravating role in excitotoxicity if a shift in the Cl^- equilibrium potential occurs during cerebral ischemia.2. We have developed an optical imaging method of [Cl^-] _i in brain slices using 6-methoxy-N-ethylquinolinium iodide (MEQ). Slices of neocortex taken from P1 … More 0-14 rats were labeled with MEQ ; [Cl^-] ^i was monitored in individual neurons during O_2-glucose deprivation. A slight decrease followed by rather abmpt increase in [Cl^-] _i was induced by O_2-glucose deprivation. The former was mediated by an inhibition of Na^+, K^+-2Cl^- cotransporter. Such a shift in [Cl^-] _i induced by O_2-glucose deprivation would alter the GABAergic inhibition and may result in imbalance between inhibitory and excitatory systems.3.3-NPA-induced [Ca^<2+>] _i transients in mixed glial/neuronal cultures were investigated using fura-2.3-NPA irreversibly increased [Ca^<2+>] _i in astrocytes, but significantly to alesser extent in neurons. The [Ca^<2+>] _i increase in astrocytes was primarily promoted by a reverse operation of the Na^+-Ca^<2+> exchanger system, whereas in neurons, it was mediated by a different mechanism. In addition, 3-NPA killed 9% of astrocytes, while only 4% of neurons. This astrocytic cell death was preceded by blebbing of membranes and by abrupt [Ca^<2+>] _i surge following sustained [Ca^<2+>] _i increase. The results indicate that astrocytes are more vulnerable than neurons to 3-NPA-induced cellular Ca^<2+> overload and toxicity. Differential metabolism in energy production between astrocytes and neurons were suggested. Less