L-NAME modulates glutamate accumulation induced by K(+)-depolarization but not by forebrain ischaemia in the rat striatum.
The accumulation of extracellular glutamate and aspartate in the striatum of rats during ischaemia was examined by perfusion with Ca(+)-free medium and treatment with the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). Male Wistar rats were subjected to 30 min ischaemia using the 4-vessel occlusion model or high K(+)-depolarization. Extracellular glutamate and aspartate were monitored by in vivo microdialysis. Perfusion with Ca(2+)-free medium and systemic administration or local perfusion of L-NAME reduced the K(+)-evoked glutamate accumulation but not the ischaemia-induced glutamate accumulation. The aspartate concentration was unaffected in both conditions. Our data suggest that the extracellular glutamate and aspartate originates from a Ca(2+)-independent pool during forebrain ischaemia and is not modulated by nitric oxide. In high K(+)-depolarization the accumulated glutamate may arise, at least in part, from enhanced vesicular release and is modulated by nitric oxide.
Ghribi
O
O
Laboratoire de Pharmacologie, Faculté des Sciences Pharmaceutiques et Biologiques, Universitè René Descartes, Paris, France.
Callebert
J
J
Plotkine
M
M
Boulu
R G
RG
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001224:Aspartic Acid / Q000378:metabolism; D002545:Brain Ischemia / Q000503:physiopathology*; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D019331:NG-Nitroarginine Methyl Ester; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism*; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D019001:Nitric Oxide Synthase; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D009467:Neuromuscular Depolarizing Agents; D001224:Aspartic Acid; D009569:Nitric Oxide; D018698:Glutamic Acid; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D011188:Potassium; D019331:NG-Nitroarginine Methyl Ester