Subcellular localization of glutamate-stimulated intracellular magnesium concentration changes in cultured rat forebrain neurons using confocal microscopy.
Glutamate can stimulate increases in intracellular magnesium concentration ([Mg2+]i) and induce neurotoxicity, both independent of Ca2+ changes. Although Mg2+ is essential within the cell, very little is known about how it is regulated, especially in neurons. Therefore we used the fluorescent indicator, magindo-1 and confocal microscopy to examine possible intracellular pools of Mg2+ in cultured neurons that can be dynamically regulated by glutamate. The magindo-1 fluorescence signal was present throughout the cell body and extends into the neuronal processes. The magindo-1 405 nm/490 nm ratio signal was similar in the cytoplasm and nucleus, suggesting that resting [Mg2+]i is uniform across the neuron. The addition of 100 microM glutamate/10 microM glycine in an extracellular Ca2+- and Na+-free buffer stimulated an increase in [Mg2+]i in both the nuclear and cytoplasmic regions of similar magnitude and duration. This glutamate exposure also stimulated a [Mg2+]i increase in neuronal processes which was inhibited by the N-methyl-D-aspartate receptor antagonist, MK-801 (10 microM). The glutamate-stimulated [Mg2+]i increase in both the cell body and neuronal processes was dependent on the extracellular Mg2+ concentration. These findings suggest glutamate-stimulated [Mg2+]i changes may not only impact cytoplasmic processes, but also directly trigger nuclear events involved, for example, in neuronal injury.
Cheng
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Department of Pharmacology, University of Pittsburgh School of Medicine, PA 15261, USA.
Reynolds
I J
IJ
D000085:Acetates; D000818:Animals; D002478:Cells, Cultured; D018698:Glutamic Acid / Q000494:pharmacology*; D007211:Indoles; D007425:Intracellular Membranes / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism*; D009994:Osmolar Concentration; D016548:Prosencephalon / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000378:metabolism*; D014018:Tissue Distribution
D000085:Acetates; D007211:Indoles; C405352:mag-indo-1 AM; D018698:Glutamic Acid; D008274:Magnesium