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Modulation of 45 Ca 2+ Influx into Cells Stably Expressing Recombinant Human NMDA Receptors by Ligands Acting at Distinct Recognition Sites
Author(s) -
Grimwood Sarah,
Gilbert Elizabeth,
Ragan C. Ian,
Hutson Peter H.
Publication year - 1996
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.1471-4159.1996.66062589.x
Subject(s) - ifenprodil , nmda receptor , receptor , glutamate receptor , agonist , chemistry , spermine , biochemistry , biology , pharmacology , enzyme
A 45 Ca 2+ influx assay has been used to investigate the pharmacology of stably expressed recombinant human NR1a/NR2A and NR1a/NR2B N ‐methyl‐ d ‐aspartate (NMDA) receptors. Inhibition of glutamate‐stimulated 45 Ca 2+ influx by six glycine‐site antagonists and inhibition of glycine‐stimulated 45 Ca 2+ influx by five glutamate‐site antagonists revealed no significant differences between affinity values obtained for NR1a/NR2A and NR1a/NR2B receptors. The polyamine site agonist spermine showed differential modulation of glutamate‐ and glycine‐stimulated 45 Ca 2+ influx for recombinant NMDA receptors, inhibiting and stimulating 45 Ca 2+ influx into cells expressing NR1a/NR2A receptors (IC 50 = 408 µ M ) and NR1a/NR2B receptors (EC 50 = 37.3 µ M ), respectively. The antagonist ifenprodil was selective for NR1a/NR2B receptors (IC 50 = 0.099 µ M ) compared with NR1a/NR2A receptors (IC 50 = 164 µ M ). The effects of putative polyamine site antagonists, redox agents, ethanol, and Mg 2+ and Zn 2+ ions were also compared between NR1a/NR2A and NR1a/NR2B receptors. This study demonstrates the use of 45 Ca 2+ influx as a method for investigating the pharmacology of the numerous modulatory sites that regulate the function of recombinant human NMDA receptors stably expressed in L(tk‐) cells.