Regulation of intracellular sodium in cultured rat hippocampal neurones.
Regulation of intracellular sodium in cultured rat hippocampal neurones.
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培养的大鼠海马神经元细胞内钠的调节。
DOI：
10.1113/jphysiol.1997.sp021951
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Ransom,BR
中科院分区：
文献类型：
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作者：
Rose,CR;Ransom,BR
1.我们使用Na+指示剂染料SBFI（钠结合苯并呋喃三甲酸酯）的荧光比率成像研究了培养的大鼠海马神经元细胞内Na+浓度（[Na+]i）的调节。2.在含3 mM K+的标准CO2/HCO 3（-）缓冲盐水中，神经元的基线[Na+]i为8.9 +/-3.8 mM（平均值+/-S.D.）。在所研究的27%的盖玻片上的神经元中观察到自发、短暂的[Na+]i增加5 mM。这些[Na+]i的增加往往是同步的附近的神经元和可逆地阻止1 μ M河豚毒素（TTX）或含10 mM Mg 2+的盐水，这表明它们是由周期性的突触偶联细胞的爆发活动。通过应用50 μ M藜芦碱打开电压门控Na+通道导致TTX敏感性[Na+]i增加25 mM。去除细胞外Na+导致[Na+]i在10 min内呈指数下降至接近零的值。通过去除细胞外K+或哇巴因应用抑制Na+，K（+）-ATP酶引起[Na+]i增加5 mM min-1。在存在或不存在CO2/HCO 3-的情况下，基线[Na+]i相似;从无CO2/HCO 3（-）-转换为CO2/HCO 3（-）-缓冲盐水，但是，[Na+]i一过性增加3 mM，表明Na（+）-依赖性Cl（-）-HCO 3-交换激活。布美他尼抑制Na（+）-K（+）-2Cl-共转运对[Na+]i无影响。4.细胞外K+浓度（[K+]o）的微小变化对神经元[Na+]i的影响很小。[K+]o升高或降低1 mM时，[Na+]i几乎没有变化。只有30%的细胞对3 min [K+] o升高至5 mM有反应。相反，长时间（≥ 10 min）[K+]o改变至6 mM或更高时，大多数细胞的稳态[Na+]i缓慢变化。5.我们的研究结果表明，[Na+]i调节培养的海马神经元和星形胶质细胞之间的几个差异。与星形胶质细胞相比，神经元中的基线[Na+]i较低，主要由Na+，K（+）-ATP酶决定，而Na（+）-依赖性Cl（-）-HCO 3-交换、Na（+）-HCO 3-共转运或Na（+）-K（+）-2Cl-共转运不起显著作用。与神经胶质细胞相反，神经元的[Na+]i仅发生微弱变化，而[K+]o也发生微小变化，这表明脑中活动诱导的[K+]o变化可能不会显著影响神经元Na+，K（+）-ATP酶活性。
1. We studied regulation of intracellular Na+ concentration ([Na+]i) in cultured rat hippocampal neurones using fluorescence ratio imaging of the Na+ indicator dye SBFI (sodium‐binding benzofuran isophthalate). 2. In standard CO2/HCO3(‐)‐buffered saline with 3 mM K+, neurones had a baseline [Na+]i of 8.9 +/‐ 3.8 mM (mean +/‐ S.D.). Spontaneous, transient [Na+]i increases of 5 mM were observed in neurones on 27% of the coverslips studied. These [Na+]i increases were often synchronized among nearby neurones and were blocked reversibly by 1 microM tetrodotoxin (TTX) or by saline containing 10 mM Mg2+, suggesting that they were caused by periodic bursting activity of synaptically coupled cells. Opening of voltage‐gated Na+ channels by application of 50 microM veratridine caused a TTX‐sensitive [Na+]i increase of 25 mM. 3. Removing extracellular Na+ caused an exponential decline in [Na+]i to values close to zero within 10 min. Inhibition of Na+,K(+)‐ATPase by removal of extracellular K+ or ouabain application evoked a [Na+]i increase of 5 mM min‐1. Baseline [Na+]i was similar in the presence or absence of CO2/HCO3‐; switching from CO2/HCO3(‐)‐free to CO2/HCO3(‐)‐buffered saline, however, increased [Na+]i transiently by 3 mM, indicating activation of Na(+)‐dependent Cl(‐)‐HCO3‐ exchange. Inhibition of Na(+)‐K(+)‐2Cl‐ cotransport by bumetanide had no effect on [Na+]i. 4. Brief, small changes in extracellular K+ concentration ([K+]o) influenced neuronal [Na+]i only weakly. Virtually no change in [Na+]i was observed with elevation or reduction of [K+]o by 1 mM. Only 30% of cells reacted to 3 min [K+]o elevations of up to 5 mM. In contrast, long [K+]o alterations (> or = 10 min) to 6 mM or greater slowly changed steady‐state [Na+]i in the majority of cells. 5. Our results indicate several differences between [Na+]i regulation in cultured hippocampal neurones and astrocytes. Baseline [Na+]i is lower in neurones compared with astrocytes and is mainly determined by Na+,K(+)‐ATPase, whereas Na(+)‐dependent Cl(‐)‐HCO3‐ exchange, Na(+)‐HCO3‐ cotransport or Na(+)‐K(+)‐2Cl‐ cotransport do not play a significant role. In contrast to glial cells, [Na+]i of neurones changes only weakly with small alterations in bath [K+]o, suggesting that activity‐induced [K+]o changes in the brain might not significantly influence neuronal Na+,K(+)‐ATPase activity.