The dose-response relationship for N-methyl-D-aspartate currents in cultured rat septal neurons: effects of magnesium ions and 2-amino-5-phosphonovaleric acid.
Dose-response relations of the peak ionic current induced by N-methyl-D-aspartate (NMDA) under Mg-free vs normal saline (1.2 mM Mg) conditions were obtained in cultured neurons dissociated from septa of fetal rat brains using the single electrode voltage clamp method. The effect of D,L-2-amino-5-phosphonovalerate (APV) on the dose-response relationship was also studied. In the Mg-free condition, the response to NMDA increased progressively with dose up to 0.2 mM, at which point the response saturated up to 1 mM NMDA (ED50 was about 70 microM). At larger doses (1-3 mM) the response increased sharply. In normal saline the response increased up to doses of 10 mM, and there was no apparent plateau. In a comparison between the depressant effects of APV and Mg ions on the peak current value, the depression caused by APV (10-30 microM) at higher NMDA concentrations was larger than that caused by Mg.
Shingai
R
R
Department of Pharmacology, Faculty of Medicine, Yamaguchi University, Ube, Japan.
Ebina
Y
Y
Nagaoka
S
S
Harada
K
K
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D008274:Magnesium / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D012686:Septal Nuclei / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D015763:2-Amino-5-phosphonovalerate; D008274:Magnesium