Blockade of nitric oxide formation does not prevent glutamate-induced neurotoxicity in neuronal cultures from rat hippocampus.
This study examined the role of nitric oxide (NO) in glutamate-induced, N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity in rat hippocampal neuronal cultures grown under serum-free conditions. Formation of cGMP was used as an indirect measure of NO formation. Neuronal cell degeneration was monitored by measuring the release of lactate dehydrogenase (LDH). Neuronal cells showed a 4-fold increase in cGMP formation and release of LDH upon exposure to 30 microM glutamate. cGMP formation was fully inhibited by 1 microM nitro-arginine (N-Arg), 100 microM hemoglobin or 1 microM MK-801. In the presence of 1 microM MK-801, glutamate induced neither cGMP formation nor neuronal cell degeneration. However, when NO formation was inhibited by means of 100 microM N-Arg, glutamate still induced neurotoxicity. Therefore, in serum-free hippocampal cultures glutamate neurotoxicity occurs notwithstanding complete inhibition of the NO-synthase enzyme by N-Arg. Our data provide evidence that NO, synthesized upon glutamate exposure, has not a primary toxic action in pure hippocampal neuronal cultures.
D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D016895:Culture Media, Serum-Free; D006152:Cyclic GMP / Q000096:biosynthesis; D003864:Depression, Chemical; D016291:Dizocilpine Maleate / Q000494:pharmacology; D005971:Glutamates / Q000633:toxicity*; D018698:Glutamic Acid; D006454:Hemoglobins / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism / Q000633:toxicity*; D019001:Nitric Oxide Synthase; D019335:Nitroarginine; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000502:physiology
D016895:Culture Media, Serum-Free; D005971:Glutamates; D006454:Hemoglobins; D016194:Receptors, N-Methyl-D-Aspartate; D019335:Nitroarginine; D009569:Nitric Oxide; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D001120:Arginine; D007770:L-Lactate Dehydrogenase; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D006152:Cyclic GMP