title: Regulation of nitric oxide synthase activity in cortical slices by excitatory amino acids and calcium.
abstract: Nitric oxide synthase (NOS) activity was determined in adult rat frontal cortex and hippocampus by measuring the conversion of L-[3H]arginine to L-[3H]citrulline. N-methyl-D-aspartate (NMDA), but not kainate or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA), stimulated NOS activity. This effect was concentration dependent (EC50 approximately 30 microM) and was inhibited by tetrodotoxin, EGTA, N omega-nitro-L-arginine (NOARG), Mg2+, phencyclidine, and (cis)-4-phosphonomethyl-2-piperidine carboxylate (CGS 19755), but not by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). NOS activity was increased to an even greater extent by the calcium ionophores ionomycin and A23187 and by depolarization with 50 mM K+. Interestingly, neither caffeine nor 1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), drugs that would be expected to increase intracellular Ca2+ concentration by release of Ca2+ from intracellular ryanodine- and inositol-1,4,5-trisphosphate-sensitive stores, respectively, had any significant effect on NOS activity. It is concluded that NOS can be activated by NMDA binding to a classic NMDA glutamate receptor subtype as well as by depolarization or other agents that increase the influx of extracellular Ca2+. The paradoxical lack of effect of caffeine, as well as the inhibitory effect of tetrodotoxin, are discussed.
authors.affiliation: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77555-1031.
authors.forename: S
authors.initials: S
authors.lastname: Alagarsamy
authors.forename: G
authors.initials: G
authors.lastname: Lonart
authors.forename: K M
authors.initials: KM
authors.lastname: Johnson
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001120:Arginine / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000201:enzymology*; D002956:Citrulline / Q000096:biosynthesis; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D019001:Nitric Oxide Synthase; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D002956:Citrulline; D013779:Tetrodotoxin; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D002118:Calcium