Excitatory and inhibitory amino acid changes in ischemic brain regions in spontaneously hypertensive rats.

Excitatory (glutamate, aspartate) or inhibitory amino acids (gamma-aminobutyric acid: GABA, taurine) and glutamine contents were examined in acutely induced cerebral ischemia in spontaneously hypertensive rats. At 20 min ischemia most of these amino acids remained unchanged, but glutamine significantly decreased by 14% in the CA3 hippocampal subfield. At 60 min ischemia glutamate significantly decreased by 14% in the CA3, aspartate by 17-26% in the CA3, cingulate cortex, septum and striatum. In contrast, GABA significantly increased by 48-106% in the cortices (frontal, parietal and cingulate), striatum and nucleus accumbens, but insignificantly in hippocampal subfields. Likewise, taurine increased in the parietal cortex and nucleus accumbens. Glutamine showed heterogeneous changes (increase in the nucleus accumbens and decrease in the CA3). Amino acid levels change during ischemia, but their changes are varied in each area, implying that different reaction of amino acids may explain the selective vulnerability to cerebral ischemia.