title: In vivo evidence for functional NMDA receptor blockade by memantine in rat hippocampal neurons.
abstract: Antagonising the NMDA (N-methyl-D: -aspartate) receptor complex is a widely hypothesised therapeutic approach in several neurodegenerative conditions, such as Alzheimer's disease. Memantine, a moderate affinity uncompetitive NMDA receptor antagonist, has been in clinical use for several years and numerous experimental data support its NMDA receptor blocking effects. It has recently been reported in transfected HEK293T cells that physiological concentrations of Mg(2+) may impart partial NMDA receptor subtype selectivity and weaken the overall inhibitory actions of memantine in NMDA receptor-mediated cellular events. In the present study, we set out to investigate the effect of intravenously applied memantine on iontophoresed NMDA-evoked firing of hippocampal CA1 neurons using in vivo conditions. Cumulative doses of memantine in the rat (4, 8 and 16 mg/kg i.v.) caused the firing rate to decrease in a dose-dependent manner to 77 ± 7, 58 ± 8 and 34 ± 12% of control, respectively, while saline application had no significant effect. We show that therapeutic doses of memantine are able to antagonize NMDA receptor-mediated activity in the principal cells of the hippocampus in vivo, i.e. in the presence of physiological concentrations of Mg(2+).
authors.affiliation: Bay Zoltán Foundation of Applied Research, BAYGEN Institute, Közép fasor 41, Szeged 6727, Hungary. szegediv@baygen.hu
authors.forename: Viktor
authors.initials: V
authors.lastname: Szegedi
authors.forename: Gábor
authors.initials: G
authors.lastname: Juhász
authors.forename: Chris G
authors.initials: CG
authors.lastname: Parsons
authors.forename: Dénes
authors.initials: D
authors.lastname: Budai
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000187:drug effects / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008559:Memantine / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D008559:Memantine
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