RESUMO
BACKGROUNDS: The importance of toxic extracellular levels of excitatory amino acids, as well as of high extracellular levels of inhibitory amino acids, is considered to be related with the pathophysiology of neuronal cell loss during cerebral ischemia. METHODS: The extracellular concentration of glutamate, glycine, and taurine in the hippocampus were determined during and after transient global ischemia in the New Zealand white rabbit. Because the cerebroprotective effects of profound hypothermia are well known and clinically widely used,we used the hypothermia group as an experimental group compared with normothermic control group in the experimental protocol. To derive a quantitative descriptor reflecting the magnitude of amino acid neurotransmitter changes with ischemia, we defined the 'taurine index' as: [glutamate]x[glycine]/[taurine]. RESULTS: Ischemia led to large increases in both excitatory (glutamate and glycine) and inhibitory amino acids(taurine) in the normothermic group. Taurine index was increased during ischemia and after reperfusion and had a close relationship with the severity of ischemia-induced neuronal damage. CONCLUSIONS: The taurine index appears to be a reliable biochemical marker to determine the severity of ischemic injury.