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Effects of N ‐Methyl‐d‐Aspartate on [Ca 2+ ] i and the Energy State in the Brain by 19 F‐ and 31 P‐Nuclear Magnetic Resonance Spectroscopy
Author(s) -
BenYoseph O.,
Bachelard H. S.,
BadarGoffer R. S.,
Dolin S. J.,
Morris P. G.
Publication year - 1990
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 - 10.1111/j.1471-4159.1990.tb03160.x
Subject(s) - phosphocreatine , extracellular , chemistry , nmda receptor , calcium , intracellular , depolarization , biophysics , analytical chemistry (journal) , medicine , biochemistry , endocrinology , energy metabolism , biology , chromatography , receptor , organic chemistry
Abstract: The effects of N ‐methyl‐d‐aspartate (NMDA) on the free intracellular Ca 2+ concentration ([Ca 2+ ] i ) and the energy state in superfused cerebral cortical slices have teen studied using 19 F‐ and 31 P‐nuclear magnetic resonance spectroscopy. [Ca 2+ ] i was measured using the calcium indicator 1,2‐bis(2‐amino‐5‐fluorophenoxy)ethane‐ N.N.N′.N′ ‐tetraacetic acid (5FBAPTA). NMDA (10 μ M ) in the absence of extracellular Mg 2+ caused the expected rise in [Ca 2+ ] i but produced an impairment of the energy state: the phosphocreatine (PCr) content was decreased by 42%, and the P i /PCr ratio was increased by 55%. There was no detectable change in ATP or free intracellular Mg 2+ concentration. Increasing the NMDA concentration in the superfusing medium to 100 or 400 μ M caused no further increase in [Ca 2+ ] i or further decrease in PCr content, but the P i /PCr ratio continued to rise. The impairment of the energy state preceded the effect on [Ca 2+ ] i , and these changes were irreversible on return to control conditions. Repeating the experiments in the presence of 1.2 m M extracellular Mg 2+ resulted in similar changes in the energy state, with no change in [Ca 2+ ] i . The possibilities that the effects were due to membrane depolarisation or to the presence of 5FBAPTA within the tissues were eliminated. The results suggest that low concentrations (10 μ M ) of NMDA produce an impaired energy state independent of the presence of extracellular Mg 2+ and that the decreased energy state is not due to the changes in [Ca 2+ ] i , which are seen only in the absence of extracellular Mg 2+ .