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N ‐Methylaspartate‐Evoked Liberation of Taurine and Phosphoethanolamine In Vivo: Site of Release
Author(s) -
Lehmann Anders,
Lazarewicz Jerzy W.,
Zeise Marc
Publication year - 1985
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.1471-4159.1985.tb05538.x
Subject(s) - taurine , liberation , chemistry , synaptosome , agonist , biochemistry , glycine , amino acid , in vivo , medicine , hippocampal formation , endocrinology , in vitro , receptor , biology , microbiology and biotechnology
The effect of N ‐methyl‐ d , l ‐aspartic acid (NMA) on extracellular amino acids was studied in the rabbit hippocampus with the brain dialysis technique. Administration of 0.5 or 5 m M NMA caused a concentration‐dependent liberation of taurine and phosphoethanolamine (PEA). Taurine increased by 1,200% and PEA by 2,400% during perfusion with 5 m M NMA whereas most other amino acids rose by 20–100%. The effect of NMA appeared to be receptor‐mediated, as coperfusion with D‐2‐amino‐5‐phosphonovaleric acid curtailed the NMA response by some 90%. The NMA‐stimulated release of taurine and PEA was suppressed when Ca 2+ was omitted and further inhibited when Co 2+ was included in the perfusion medium. The effect of NMA was mimicked by the endogenous NMA agonist quinolinic acid and the partial NMA agonist d , l ‐ cis ‐2,3‐piperidine dicarboxylic acid. Although the NMA‐evoked release of taurine and PEA was Ca 2+ ‐dependent in vivo, NMA had no effect on Ca 2+ accumulation in hippocampal synaptosomes. The previously reported NMA‐induced activation of dendritic Ca 2+ spikes and the lack of effect on synaptosomal Ca 2+ uptake suggest that taurine and PEA are released from sites other than nerve terminals, possibly from dendrosomatic sites. This notion was strengthened by the absence of an effect of NMA on the efflux of radiolabelled taurine from hippocampal synaptosomes. In contrast, high K + stimulated synaptosomal uptake of Ca 2+ and release of taurine.