Extracellular glutamate concentration in hippocampal slice
Extracellular glutamate concentration in hippocampal slice
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DOI：
10.1523/jneurosci.3009-07.2007
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发表时间：
2007-09-05
影响因子：
5.3
通讯作者：
Jahr, Craig E.
中科院分区：
文献类型：
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作者：
Herman, Melissa A.;Jahr, Craig E.
由囊泡胞吐引起的突触谷氨酸瞬变叠加在细胞外间隙中谷氨酸的低基线浓度上。报告的基线谷氨酸浓度值范围高达4 μ M。如果谷氨酸以低微摩尔浓度存在，许多受体，特别是高亲和力NMDA受体（NMDAR），将被激活或脱敏，改变神经元的兴奋性。使用急性海马切片中CA1锥体细胞表达的NMDAR来监测细胞外谷氨酸，我们发现其基线浓度低得多，接近25 nM。此外，灌流低微摩尔浓度的谷氨酸对神经元没有影响，表明谷氨酸转运阻止了切片内受体的进入。然而，等效浓度的NMDA，非转运激动剂，去极化神经元显着。我们认为，环境浓度的谷氨酸在体内也在纳摩尔范围内，太低，导致显着的受体激活。
Synaptic glutamate transients resulting from vesicular exocytosis are superimposed on a low baseline concentration of glutamate in the extracellular space. Reported values of baseline glutamate concentrations range up to 4 mu M. If glutamate were present tonically at low micromolar concentrations, many receptors, especially the high-affinity NMDA receptors ( NMDARs), would be activated or desensitized, altering neuronal excitability. Using NMDARs expressed by CA1 pyramidal cells in acute hippocampal slices to monitor extracellular glutamate, we find that its baseline concentration is much lower, near 25 nM. In addition, superfusion of low micromolar concentrations of glutamate had no effect on neurons, indicating that glutamate transport prevents access to receptors within the slice. However, equipotent concentrations of NMDA, a nontransported agonist, depolarized neurons dramatically. We suggest that ambient concentrations of glutamate in vivo are also in the nanomolar range and are too low to cause significant receptor activation.