AMMONIUM ION INHIBITION OF EVOKED RELEASE OF ENDOGENOUS GLUTAMATE FROM HIPPOCAMPAL SLICES |
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Authors: | Anders Hamberger Bo Hedquist Britta Nyström |
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Institution: | Institute of Neurobiology, University of Göteborg, Fack, S-400 33 Göteborg, Sweden |
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Abstract: | Abstract— The effect of pathophysiological levels (2-5 m m ) of ammonium chloride on the efflux of endogenous and exogenous 14C]glutamate from hippocampal slices was studied. The evoked release of glutamate which occurs dring tissue depolarization with 56 m m -KCl was greatly reduced when the tissue had been exposed to NH4Cl for 40–80 min. This effect was seen whether or not glutamine (0.5 m m ) was present in the incubation medium. The effect was completely reversible. The spontaneous efflux and the evoked release of 14C]glutamate was, on the contrary, completely unaltered after exposure of the slice to ammonium ions. Nigher (20–36 m m ) amounts of NH4Cl evoked a release of 14C]glutamate from the crude mitochondrial fraction, as did high concentrations of KCl. The results are discussed in relation to the compartmentation of glutamate metabolism and the pathogenesis of hepatic coma. |
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