IMPROVED METHOD FOR THE MEASUREMENT OF GLUTAMATE AND ASPARTATE USING CAPILLARY ELECTROPHORESIS WITH LASER-INDUCED FLUORESCENCE DETECTION AND ITS APPLICATION TO BRAIN MICRODIALYSIS

We have previously published data on the analysis of glutamate in micr odialysis samples using a commercially availble CE apparatus. Here we demonstrate further improvements in the analysis of both glutamate and aspartate from very small volume microdialysates. The limit of detect ion of our system has been increased to 10(-9) M for both glutamate an d aspartate. This permits microdialysis sampling time to be reduced to 2 min, thus improving the temporal resolution of microdialysis sampli ng. Concurrently, migration time has also been reduced such that resol ution of both amino acids can be achieved inside 2 min. This new analy tical method has been applied to the measurement of the EAA from micro dialysis samples from the dentate gyrus of the hippocampus. Extracellu lar concentrations of both glutamate and aspartate increased to a maxi mum of 5- and 4.5-fold of preinfusion values, respectively, during inf usion of 100 mM K+ through the microdialysis probe. This is consistent with the depolarization-evoked release of both amino acids from this brain region. (C) 1997 Elsevier Science B.V.