Kainate-induced stimulation of amino acid release from primary astroglial cultures of the rat hippocampus.
The effects of the excitatory amino acid analogs kainate (KA) and N-methyl-d-aspartate (NMDA) on release of amino acids from astrocytes in primary culture were investigated. Under basal conditions, glutamine was present in the medium at 15 ?M. The levels of serine and taurine were 1.5 and 2.0 ?M, respectively, while the concentration of other amino acids was below 1 ?M. At 10 ?M, KA did not affect amino acid release, whereas 100 ?M KA enhanced glutamine release by 34% and taurine release by 85%. At 1 mM, KA stimulated the release of all amino acids measured. However, while most amino acids increased by 50-150%, glutamate and aspartate were elevated by more than 3000%. The effect of KA was greatly reduced by 1 mM kynurenate, an excitatory amino acid receptor antagonist. 1 mM NMDA did not stimulate amino acid release from the cultures. The results indicate that astrocytes are endowed with KA-receptive sites, but they do not seem to possess NMDA receptors.
Lehmann
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A
Institute of Neurobiology, University of Göteborg, Göteborg, Sweden.
Hansso
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E