The excitatory synaptic transmission is mediated by glutamate in neuronal networks of the mammalian brain. In addition to the synaptic glutamate, extra-synaptic glutamate is known to modulate the neuronal activity. In neuronal networks, glutamate uptake is an important role of neurons and glial cells for lowering the concentration of extracellular glutamate and to avoid the excitotoxicity by glutamate. Monitoring the spatial distribution of intracellular glutamate is important to study the uptake of glutamate, but the approach has been hampered by the absence of appropriate glutamate analogs that report the localization of glutamate. Deuterium-labeled glutamate (GLU-D) is a promising tracer for monitoring the intracellular concentration of glutamate, but physiological properties of GLU-D have not been studied. Here we study the effects of extracellular GLU-D for the neuronal activity by using primary cultured rat hippocampal neurons that form neuronal networks on microelectrodes array. The frequency of firing in the spontaneous activity of neurons increased with the increasing concentration of extracellular GLU-D. The frequency of synchronized burst activity in neurons increased similarly as we observed in the spontaneous activity. These changes of the neuronal activity with extracellular GLU-D were suppressed by antagonists of glutamate receptors. These results suggest that GLU-D can be used as an analog of glutamate with equivalent effects for facilitating the neuronal activity. We anticipate GLU-D developing as a promising analog of glutamate for studying the dynamics of glutamate during neuronal activity.

中文翻译：

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氘代谷氨酸介导的微电极阵列上的神经元活性。

兴奋性突触传递是由哺乳动物大脑神经元网络中的谷氨酸介导的。除突触谷氨酸外，突触外谷氨酸还可以调节神经元活性。在神经元网络中，谷氨酸的摄取对于降低细胞外谷氨酸的浓度并避免谷氨酸的兴奋性毒性是神经元和神经胶质细胞的重要作用。监测细胞内谷氨酸的空间分布对于研究谷氨酸的摄取很重要，但是由于缺少报告谷氨酸定位的合适谷氨酸类似物，该方法受到阻碍。氘标记的谷氨酸（GLU-D）是用于监测细胞内谷氨酸浓度的有前途的示踪剂，但尚未研究GLU-D的生理特性。在这里，我们通过使用在微电极阵列上形成神经元网络的原代培养的大鼠海马神经元来研究细胞外GLU-D对神经元活性的影响。随着细胞外GLU-D浓度的增加，神经元自发活动的放电频率也随之增加。与我们在自发活动中观察到的相似，神经元中同步爆发活动的频率增加。谷氨酸受体拮抗剂可抑制细胞外GLU-D引起的神经元活性的这些变化。这些结果表明，GLU-D可以用作谷氨酸的类似物，具有促进神经元活性的等效作用。我们预期GLU-D有望发展成为一种有前途的谷氨酸类似物，用于研究神经元活动期间谷氨酸的动力学。