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Activation of Glutamate Receptors Stimulates the Formation of Nitrite in Synaptosomes from Rat Cerebellum
Author(s) -
Gorbunov Nikolai,
Esposito Ennio
Publication year - 1994
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1994.62062205.x
Subject(s) - metabotropic glutamate receptor , nmda receptor , metabotropic glutamate receptor 5 , agonist , metabotropic receptor , glutamate receptor , metabotropic glutamate receptor 1 , chemistry , ionotropic effect , biochemistry , receptor
Synaptosomes from rat cerebellum were used to investigate the involvement of different glutamate receptor subtypes in the control of the synthesis of nitric oxide (NO), measured as its breakdown product nitrite (NO 2 ‐ ). Synaptosomes incubated in the presence of NAD|PH and l ‐arginine produced measurable levels of NO 2 ‐ , which were reduced by addition of N ω‐nitro‐ l ‐arginine methyl ester, an inhibitor of nitric oxide synthase. The selective ionotropic glutamate receptor agonist N ‐methyl‐ d ‐aspartate (NMDA) induced a pronounced increase in NO 2 ‐ formation, which was prevented by N ω‐nitro‐ l ‐arginine methyl ester and by the specific NMDA receptor antagonist D l ‐2‐amino‐5‐phosphonovaleric acid (AP‐5). The NMDA‐induced increase in NO 2 ‐ formation was blocked by chelation of extracellular Ca 2+ with EGTA. Both l ‐glutamate and the selective agonist for the metabotropic glutamate receptors (β)‐1‐aminocyclopentane‐ trans ‐1,3‐dicarboxylic acid raised NO 2 ‐ production, which retumed to control levels after addition of Nω‐nitro‐ l ‐arginine methyl ester. The selective glutamate ionotropic receptor agonist (R,S)‐α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionic acid did not cause any change in NO 2 formation. The stimulatory effect of l ‐glutamate was blocked by the metabotropic glutamate receptor antagonist D l ‐2‐amino‐4‐phosphonobutyric acid but was unaffected by the selective NMDA receptor blocker AP‐5. Removal of extracellular Ca 2+ by EGTA did not affect the action of l ‐glutamate; whereas W‐7, an inhibitor of calmodulin, and dantrolene, a compound that blocks the mobilization of Ca 2+ from intracellular stores, abolished the effect of l ‐glutamate on NO 2 ‐ formation. It is suggested that stimulation of ionotropic NMDA receptors activates NO metabolism by causing an influx of Ca 2+ from the extracellular space, whereas activation of metabotropic receptors by l ‐glutamate provokes a mobilization of Ca 2+ from intracellular stores, which stimulates nitric oxide synthase activity by forning Ca 2+ /calmodulin complexes.