Copper Modulation of NMDA Responses in Mouse and Rat Cultured Hippocampal Neurons

Authors

  • Viktorie Vlachová,

    1. Institute of Physiology, Academy of Sciences of the Czech Republic, Videňská 1083, 142 20 Prague 4, Czech Republic
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  • Hana Zemková,

    1. Institute of Physiology, Academy of Sciences of the Czech Republic, Videňská 1083, 142 20 Prague 4, Czech Republic
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  • Ladislav Vyklický Jr

    Corresponding author
    1. Institute of Physiology, Academy of Sciences of the Czech Republic, Videňská 1083, 142 20 Prague 4, Czech Republic
    2. Laboratory of Cellular and Molecular Neurophysiology, Building 49, Room 5A78, NICHD, National Institutes of Health, Maryland 20892, USA
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Ladislav Vyklický, Jr, Institute of Physiology AS CR, Videňská 1083, 142 20 Prague 4, Czech Republic

Abstract

The effect of Cu2+ on NMDA receptors was studied in cultured mouse and rat hippocampal neurons using whole-cell patch-clamp and a fast perfusion system. Analysis of the Cu2+ concentration-response curve for inhibition of NMDA-induced currents suggests that free Cu2+ directly inhibits NMDA receptors with an IC50 of 0.27 μM. Cu2+ was ineffective in blocking NMDA receptor activity when complexed with NMDA or glycine; NMDA-Cu2+ and glycine-Cu2+ complexes acted as agonists of similar potency to the free amino acids. The inhibition by Cu2+ (10–100 μM) of responses to 10 μM NMDA was essentially voltage-independent. The onset of inhibition by 100 μM Cu2+ of responses to 2 FM glutamate acting at NMDA receptors was significantly faster than NMDA receptor deactivation evoked by a sudden decrease in the concentration of glycine or glutamate, or of both agonists. This suggests that CU2+ acts as a non-competitive antagonist, and does not directly interfere with the binding of glutamate or glycine to their recognition sites on the NMDA receptor complex. In the absence of NMDA the apparent association rate constant for binding of Cu2+ to NMDA receptors, calculated from the rate of onset of block by Cu2+ of test responses to NMDA, was 19 times slower than in the presence of 30 μM NMDA, suggesting that Cuz+ interacts preferentially with agonist-bound receptors. Our results show that Cu2+ is a potent inhibitor of NMDA receptor-mediated responses.

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