Glutamate‐induced calcium increase mediates magnesium release from mitochondria in rat hippocampal neurons |
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Authors: | Yutaka Shindo Ai Fujimoto Kohji Hotta Koji Suzuki Kotaro Oka |
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Institution: | 1. Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa, Japan;2. Center for Science and Technology for Designing Functions, School of Integrated Design Engineering, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa, Japan |
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Abstract: | Excess administration of glutamate is known to induce Ca2+ overload in neurons, which is the first step in excitotoxicity. Although some reports have suggested a role for Mg2+ in the excitotoxicity, little is known about its actual contribution. To investigate the role of Mg2+ in the excitotoxicity, we simultaneously measured intracellular Ca2+ and Mg2+, using fluorescent dyes, Fura red, a fluorescent Ca2+ probe, and KMG‐104, a highly selective fluorescent Mg2+ probe developed by our group, respectively. Administration of 100 μM glutamate supplemented with 10 μM glycine to rat hippocampal neurons induced an increase in intracellular Mg2+ concentration (Mg2+]i). Extracellular Mg2+ was not required for this glutamate‐induced increase in Mg2+]i, and no increase in intracellular Ca2+ concentration (Ca2+]i) or Mg2+]i was observed in neurons in nominally Ca2+‐free medium. Application of 5 μM carbonyl cyanide p‐(trifluoromethoxy) phenylhydrazone (FCCP), an uncoupler of mitochondrial inner membrane potential, also elicited increases in Ca2+]i and Mg2+]i. Subsequent administration of glutamate and glycine following FCCP treatment did not induce a further increase in Mg2+]i but did induce an additive increase in Ca2+]i. Moreover, the glutamate‐induced increase in Mg2+]i was observed only in mitochondria localized areas. These results support the idea that glutamate is able to induced Mg2+ efflux from mitochondria to the cytosol. Furthermore, pretreatment with Ru360, an inhibitor of the mitochondrial Ca2+ uniporter, prevented this Mg2+]i increase. These results indicate that glutamate‐induced increases in Mg2+]i result from the Mg2+ release from mitochondria and that Ca2+ accumulation in the mitochondria is required for this Mg2+ release. © 2010 Wiley‐Liss, Inc. |
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Keywords: | excitotoxicity Mg2+ KMG‐104 hippocampus fluorescent imaging |
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