Simultaneous determination of basal and evoked output levels of aspartate, glutamate, taurine and 4-aminobutyric acid during microdialysis and from superfused brain slices.

A HPLC method, involving pre-column derivatisation with o-phthalaldehyde and fluorescence detection, is described. It allows the resolution of aspartate, glutamate, taurine and GABA, in a single run with detection limits of 3.2, 1.7, 1.4 and 2 fmol/microl of perfusate, respectively. It is sufficiently sensitive and rapid (15 min) for the determination "on line" of the four amino acids in perfusates obtained during in vivo microdialysis experiments. The procedure has been used to determine basal, K+ - or veratridine-stimulated release of these amino acids in different brain areas during microdialysis and from perfused tissue slices.