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。缺氧缺糖时，锥体细胞内[Ca^&lt；2+&gt；]_i受到监测。II/III层神经元的[Ca^&lt；2+&gt；]_i较IV、V或VI层显著增加，板层[Ca^&lt；2+&gt；]_i升高主要由NMDA受体介导。在O_2-葡萄糖缺乏时，GABA也可引起细胞内[Ca~(2+)]_i升高。在Cl~-梯度降低后，GABA通过NMDA受体通道引起[Ca~(2+)&gt；]_i显著升高。这表明在缺血时失去正常的氯离子梯度可能是GABA能抑制减弱和/或逆转的基础。因此，如果在脑缺血过程中发生氯离子平衡电位的变化，GABA可能在兴奋性毒性中起到加重作用。我们用6-甲氧基-N-乙基喹啉碘(MEQ)建立了脑片中[Cl~-]_i的光学成像方法。取自P1…的新皮质切片更多的0-14只大鼠被MEQ标记，在O_2-葡萄糖剥夺过程中，在单个神经元上监测到[Cl^-]^i。O_2-葡萄糖剥夺可引起细胞内[Cl~-]_i轻度降低，而后轻度升高。前者是通过抑制Na~(++)，K~(++)-2Cl~(-)共转运体介导的。在混合培养的神经胶质细胞中，用Fura-2.3-NPA不可逆地增加星形胶质细胞的[Ca^&lt；2+&gt；]_i，但显著降低神经元的[Ca^&lt；2+&gt；]_i。星形胶质细胞内[Ca~(2+)]_i的升高主要由Na~(++)-Ca~(2+)&gt；交换系统的反向操作所促进，而在神经元中则是由不同的机制介导的。此外，3-NPA杀死了9%的星形胶质细胞，而只杀死了4%的神经元。在这种星形细胞死亡之前，伴随着细胞膜的起泡和持续的[Ca^&lt；2+&gt；]_i激增。结果表明，星形胶质细胞比神经元更容易受到3-NPA诱导的细胞内钙超载和毒性的影响。星形胶质细胞和神经元之间在能量产生方面存在差异代谢。较少

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