Changes of monoamines, purines and amino acids in rat striatum as measured by intercerebral microdialysis during ischemia/reperfusion.

The aim of this study was to determine the time course of changes in extracellular fluid (ECF) concentrations of purines, amino acids, monoamines, and their metabolites in the striatum of rats during ischemia and reperfusion, using intracerebral microdialysis as the sampling technique. In rats subjected to 20 min forebrain ischemia by four-vessel occlusion, the concentrations of adenosine (Ade), inosine (Ino) and hypoxanthine (Hyp) were found to rise markedly. These changes were accompanied by dramatically elevated levels of aspartate (Asp), glutamate (Glu), taurine (Tau), gamma-aminobutyric acid (GABA), dopamine (DA) and norepinephrine (NE), all of which gradually returned to baseline following reperfusion. Concomitantly, the levels of metabolite 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxyindole-3-acetic acid (5-HIAA) and xanthine (Xan) decreased during ischemia and gradually recovered 60-90 min after reperfusion. It was concluded that during global brain ischemia, the ECF is flooded with both potentially harmful (e.g. Asp, Glu, DA) and protective (e.g. Tau, GABA, Ade) agents.