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

1. 取P7-14大鼠新皮质切片，用fura-2标记。在o_2 -葡萄糖剥夺过程中监测锥体细胞的[Ca^<2+>] _i。第II/III层神经元的[Ca^<2+>] _i明显高于第IV、V、vi层神经元。[Ca^<2+>] _i升高的层间差异主要是由NMDA受体介导的。在o_2 -葡萄糖剥夺过程中，GABA也可能增加[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。这表明缺血期间正常Cl^-梯度的丧失可能是gaba能抑制减少和/或逆转的基础。因此，如果脑缺血时Cl^-平衡电位发生改变，GABA可能在兴奋性毒性中起加重作用。我们利用6-甲氧基- n -乙基碘化喹啉（MEQ）建立了脑切片[Cl^-] _i的光学成像方法。0 ~ 14只大鼠进行MEQ标记；[Cl^-] ^i在o_2 -葡萄糖剥夺过程中被监测。o_2 -葡萄糖剥夺诱导[Cl^-] _i略微下降，随后又相当明显地增加。前者通过抑制Na^+， K^+- 2cl ^-共转运体介导。在混合胶质/神经元培养中，3.3- npa诱导的[Ca^<2+>] _i瞬态在星形胶质细胞中不可逆地增加，但在神经元中显著增加的程度较低。在星形胶质细胞中，[Ca^<2+>] _i的增加主要是由Na^+-Ca^<2+>交换系统的反向操作促进的，而在神经元中，这是由不同的机制介导的。3-NPA对星形胶质细胞的杀伤率为9%，而对神经元的杀伤率仅为4%。这种星形细胞死亡之前是膜的起泡和持续的[Ca^<2+>] _i升高后突然的[Ca^<2+>] _i激增。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+>过载和毒性的影响。星形胶质细胞和神经元之间的能量产生代谢存在差异。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