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Nondestructive Detection of Glutamate by 1H Nuclear Magnetic Resonance Spectroscopy in Cortical Brain Slices from the Guinea Pig: Evidence for Changes in Detectability During Severe Anoxic Insults
Author(s) -
Kauppinen Risto A.,
Williams Stephen R.
Publication year - 1991
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.1471-4159.1991.tb08271.x
Subject(s) - glutamate receptor , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , intracellular , glutamic acid , chemistry , proton nmr , amino acid , neurotransmitter , biochemistry , slice preparation , biophysics , biology , in vitro , physics , receptor
31 P and 1 H nuclear magnetic resonance spectroscopy (NMR) was used to study the metabolism of intact superfused cortical brain slices during normoxia and anoxia. Attention was focused on quantification of 1 H NMR‐detected glutamate by a water‐suppressed spin‐echo method, using N‐acetyl aspartate as an internal concentration reference. To quantify the 1 H NMR signals, the spin‐spin relaxation times and saturation effects were estimated for given metabolites. In addition, absolute concentrations of metabolites were determined by biochemical methods from acid extracts of the preparations after NMR experiments. Under aerobic conditions, 1 H NMR detected 79% of the glutamate determined biochemically from the brain slice extracts. During anoxia in the absence of glucose when a severe energetic failure was evident, both 1 H NMR and biochemical assays gave closely matching levels for glutamate. We conclude that in the brain cortex 21% of glutamate is located in an intracellular compartment in which this amino acid does not contribute to the 1 H NMR signal. However, during severe anoxia an intracellular reorganization occurs increasing the detectability of this amino acid neurotransmitter by NMR.