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Differences in magnesium and calcium effects on N-methyl-D-aspartate- and quisqualate-induced decreases in extracellular sodium concentration in rat hippocampal slices.
Exp Brain Res. 1988; 71(2):425-30.EB

Abstract

Decreases in extracellular sodium concentration [(Na+]o) and associated slow negative field potentials (fp's) were monitored with double barreled sodium sensitive/reference microelectrodes in area CA1 of rat hippocampal slices during iontophoretic application of the glutamate receptor agonists N-methyl-D-aspartate (NMDA) and quisqualate (quis). The effects of lowering [Ca2+]o on these signals were compared to those of lowering [Mg2+]o. Both NMDA- and quis-induced decreases in [Na+]o of up to 60 mM and in the fp's of up to 8 mV. Decreasing [Mg2+]o enhanced NMDA-induced signals, whereas quis-induced signals were unaffected. Lowering [Ca2+]o also enhanced NMDA signals, although somewhat less than lowering [Mg2+]o. This effect was still present, even when voltage dependent Na+ currents were blocked by 10(-7) tetrodotoxin. Interestingly, quis-induced signals could be enhanced in a low Ca2+ medium as well, but only when high quis concentrations were used. The results suggest that, during the sorts of large decreases of [Ca2+]o observed during seizure activity, activation of NMDA receptors is facilitated.

Authors+Show Affiliations

Institut für normale und pathologische Physiologie, Universität Köln, Federal Republic of Germany.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

2844578

Citation

Köhr, G, and U Heinemann. "Differences in Magnesium and Calcium Effects On N-methyl-D-aspartate- and Quisqualate-induced Decreases in Extracellular Sodium Concentration in Rat Hippocampal Slices." Experimental Brain Research, vol. 71, no. 2, 1988, pp. 425-30.
Köhr G, Heinemann U. Differences in magnesium and calcium effects on N-methyl-D-aspartate- and quisqualate-induced decreases in extracellular sodium concentration in rat hippocampal slices. Exp Brain Res. 1988;71(2):425-30.
Köhr, G., & Heinemann, U. (1988). Differences in magnesium and calcium effects on N-methyl-D-aspartate- and quisqualate-induced decreases in extracellular sodium concentration in rat hippocampal slices. Experimental Brain Research, 71(2), 425-30.
Köhr G, Heinemann U. Differences in Magnesium and Calcium Effects On N-methyl-D-aspartate- and Quisqualate-induced Decreases in Extracellular Sodium Concentration in Rat Hippocampal Slices. Exp Brain Res. 1988;71(2):425-30. PubMed PMID: 2844578.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Differences in magnesium and calcium effects on N-methyl-D-aspartate- and quisqualate-induced decreases in extracellular sodium concentration in rat hippocampal slices. AU - Köhr,G, AU - Heinemann,U, PY - 1988/1/1/pubmed PY - 1988/1/1/medline PY - 1988/1/1/entrez SP - 425 EP - 30 JF - Experimental brain research JO - Exp Brain Res VL - 71 IS - 2 N2 - Decreases in extracellular sodium concentration [(Na+]o) and associated slow negative field potentials (fp's) were monitored with double barreled sodium sensitive/reference microelectrodes in area CA1 of rat hippocampal slices during iontophoretic application of the glutamate receptor agonists N-methyl-D-aspartate (NMDA) and quisqualate (quis). The effects of lowering [Ca2+]o on these signals were compared to those of lowering [Mg2+]o. Both NMDA- and quis-induced decreases in [Na+]o of up to 60 mM and in the fp's of up to 8 mV. Decreasing [Mg2+]o enhanced NMDA-induced signals, whereas quis-induced signals were unaffected. Lowering [Ca2+]o also enhanced NMDA signals, although somewhat less than lowering [Mg2+]o. This effect was still present, even when voltage dependent Na+ currents were blocked by 10(-7) tetrodotoxin. Interestingly, quis-induced signals could be enhanced in a low Ca2+ medium as well, but only when high quis concentrations were used. The results suggest that, during the sorts of large decreases of [Ca2+]o observed during seizure activity, activation of NMDA receptors is facilitated. SN - 0014-4819 UR - https://www.unboundmedicine.com/medline/citation/2844578/Differences_in_magnesium_and_calcium_effects_on_N_methyl_D_aspartate__and_quisqualate_induced_decreases_in_extracellular_sodium_concentration_in_rat_hippocampal_slices_ DB - PRIME DP - Unbound Medicine ER -