Simultaneous determination of glutamate and aspartate in rat periaqueductal gray matter microdialysates by capillary electrophoresis with laser-induced fluorescence

This study presented a capillary zone electrophoresis (CZE) method for the analysis of trace amount of neurotransmitters glutamate (Glu) and aspartate (Asp) in the microdialysates of rat periaqueductal gray matter (PAG). Glu and Asp were derivatized with the fluorescent agent 5-carboxyfluorescein N-succinimidyl ester (CFSE) for the first time and detected by laser-induced fluorescence (LIF) after separation by CZE. The concentration detection limits (S/N = 2) were 6.9 × 10−10 M and 8.1 × 10−10 M for Glu and Asp, respectively. The repeatability (expressed as RSD) of the migration times of CFSE–amino acid were better than 0.5%, and not higher than 1.5% even over the period of 1 month. This method was applied to quantify Glu and Asp in rat PAG microdialysates with the treatment of formalin injection, and the measured basal concentrations of Glu and Asp were (22.4 ± 1.6) × 10−6 M and (0.9 ± 0.1) × 10−6 M, respectively.