Glutamate receptor agonists stimulate nitric oxide synthase in primary cultures of cerebellar granule cells.
The glutamate receptor agonist N-methyl-D-aspartate (NMDA) stimulated a rapid, extracellular Ca(2+)-dependent conversion of [3H]arginine to [3H]citrulline in primary cultures of cerebellar granule cells, indicating receptor-mediated activation of nitric oxide (NO) synthase. The NMDA-induced formation of [3H]citrulline reached a plateau within 10 min. Subsequent addition of unlabeled L-arginine resulted in the disappearance of 3H from the citrulline pool, indicating a persistent activation of NO synthase after NMDA receptor stimulation. Glutamate, NMDA, and kainate, but not quisqualate, stimulated both the conversion of [3H]arginine to [3H]citrulline and cyclic GMP accumulation in a dose-dependent manner. Glutamate and NMDA showed similar potencies for the stimulation of [3H]citrulline formation and cyclic GMP synthesis, respectively, whereas kainate was more potent at inducing cyclic GMP accumulation than at stimulating [3H]citrulline formation. Both the [3H]arginine to [3H]citrulline conversion and cyclic GMP synthesis stimulated by NMDA were inhibited by the NMDA receptor antagonist MK-801 and by the inhibitors of NO synthase, NG-monomethyl-L-arginine (MeArg) and NG-nitro-L-arginine (NOArg). However, MeArg, in contrast to NOArg, also potently inhibited [3H]arginine uptake. Kainate (300 microM) stimulated 45Ca2+ influx to the same extent as 100 microM NMDA, but stimulated [3H]citrulline formation to a much lesser extent, which suggests that NO synthase is localized in subcellular compartments where the Ca2+ concentration is regulated mainly by the NMDA receptor.
Fidia-Georgetown Institute for the Neurosciences, Georgetown University School of Medicine, Washington, D.C. 20007.
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Costa
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Wroblewski
D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D002956:Citrulline / Q000096:biosynthesis; D006152:Cyclic GMP / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism / Q000494:pharmacology; D018698:Glutamic Acid; D006098:Granulocytes / Q000378:metabolism*; D007608:Kainic Acid / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology; D019001:Nitric Oxide Synthase; D016318:Quisqualic Acid / Q000494:pharmacology; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000502:physiology*
D005971:Glutamates; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D002956:Citrulline; D018698:Glutamic Acid; D016202:N-Methylaspartate; D016318:Quisqualic Acid; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D006152:Cyclic GMP; D007608:Kainic Acid; D002118:Calcium