Glutamate-mediated neuroprotection against N-methyl-D-aspartate toxicity: a role for metabotropic glutamate receptors.
We studied N-methyl-D-aspartate-induced cell death in organotypic hippocampal slices from seven-day-old Wistar rat pups cultured for 12-14 days in a medium containing no added glutamate. Propidium iodide fluorescence intensity was used as an indicator of cell death measured with the help of confocal microscopy. Exposure of slices for 2h to L-glutamate (1-500 microM) prior to the N-methyl-D-aspartate challenge significantly reduced N-methyl-D-aspartate-induced cell death. Glutamate at 10 and 500 microM concentrations was highly protective against N-methyl-D-aspartate-induced cell death, but was less protective at the 1 microM concentration. The protection was not blocked by the Na(+) channel blocker tetrodotoxin (1 microM), the N-methyl-D-aspartate receptor antagonist D-2-amino-5-phosphonopentanoic acid (20 microM) or the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (20 microM). 1S, 3R-1-Aminocyclopentane-trans-1,3-dicarboxylic acid, an agonist at metabotropic glutamate receptor types 1, 2/3 and 5, was protective at 100 microM but not at 50 microM. In contrast, the ionotropic glutamate receptor agonist aspartate (250 microM) facilitated N-methyl-D-aspartate toxicity. Treatment of slices with the protein kinase C inhibitor staurosporine (0.2 microM) or antisense oligonucleotide (10nM, 72 h) that selectively inhibits metabotropic glutamate receptor type 5 synthesis significantly reduced glutamate protection. These results suggest that ambient glutamate may reduce nerve cell susceptibility to injury caused by excessive N-methyl-D-aspartate receptor activation by acting at metabotropic glutamate receptors linked to protein kinase C.
Adamchik
Y
Y
Department of Physiology and Playfair Neuroscience Unit, University of Toronto, Ontario, M5T 2S8, Toronto, Canada.
Baskys
A
A
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D003515:Cycloleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D006624:Hippocampus / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D016202:N-Methylaspartate / Q000633:toxicity*; D009474:Neurons / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects; D018696:Neuroprotective Agents / Q000494:pharmacology*; D020319:Oligodeoxyribonucleotides, Antisense; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018696:Neuroprotective Agents; D020319:Oligodeoxyribonucleotides, Antisense; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D001224:Aspartic Acid; D018698:Glutamic Acid; D013779:Tetrodotoxin; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione