Lack of interaction between nitric oxide and the redox modulatory site of the NMDA receptor.
1. The inhibitory effects of nitric oxide (NO) on N-methyl-D-aspartate (NMDA) receptor function have been proposed to be mediated via the interaction of this gas with a redox-sensitive thiol moiety on the receptor. Here, we evaluated this suggested mechanism by examining the actions of various NO donors on native neuronal receptors as well as in wild-type and cysteine-mutated recombinant NMDA receptors expressed in Chinese hamster ovary (CHO) cells. 2. The NO donor N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydraxino)ethanamine (NOC-12; 100 microM) produced a rapid and readily reversible inhibition of whole-cell currents induced by NMDA (30 microM) in cultured cortical neurons. The inhibition was apparent at all holding potentials, though a more pronounced block was observed at negative voltages. The effects of NOC-12 disappeared when the donor was allowed to expire. A similar receptor block was observed with another NO-releasing agent, S-nitroso-N-acetylpenicillamine (SNAP; 1 mM). 3. The blocking effects of NO released by SNAP, 3-morpholinosydnonimine (SIN-1; 1 mM), and 3-[2-hydroxy-1-(1-methylethyl)-2-nitrosohydrazino]-1-propanamin e (NOC-5; 100 microM) on currents mediated by recombinant NRI/NR2B receptors were virtually indistinguishable from those observed on native receptors. Furthermore, mutating cysteines 744 and 798 of NR1, which constitute the principal redox modulatory site of the NR1/NR2B receptor configuration, did not affect the inhibition produced by NO. 4. The NR2A subunit may contribute its own redox-sensitive site. However, the effects of NO on NR1/NR2A receptors were very similar to those seen for all other receptor configurations evaluated. Hence, we conclude that NO does not exert its inhibition of NMDA-induced responses via a modification of any of the previously described redox-sensitive sites on the receptor.
Department of Neurobiology, University of Pittsburgh School of Medicine, Pennsylvania 15261, USA. redox@pitt.edu
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D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics
D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; C118603:NOC 12; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; C110881:S-nitro-N-acetylpenicillamine; D009569:Nitric Oxide; C002385:linsidomine; D016202:N-Methylaspartate; D008981:Molsidomine; D010396:Penicillamine