Brain glutamate monitoring by microdialysis and separation methods with a special focus on capillary electrophoresis with laser-induced fluorescence detection

Abstract

The in vivo monitoring of extracellular brain glutamate, i.e., of the glutamate fraction potentially acting on receptors, is mostly performed by brain microdialysis coupled to a separation micro-method, such an approach offering high chemical selectivity combined to good anatomical and temporal resolution. Among the two separation micro-methods used to determine glutamate in brain microdialysates, namely liquid chromatography and capillary electrophoresis, only the latter one, especially when coupled to laser-induced fluorescence detection, can allow to routinely analyze glutamate in low-volume (<1 μL) microdialysates for high temporal resolution (≤ 1 min) monitoring of fast neurobiological events. This chapter will present detailed capillary electrophoresis with laser-induced fluorescence detection protocols for the monitoring of glutamate in brain microdialysate. Various aspects of the technology, including sample derivatization, injection procedures, modes of separation and their effects on analytical performance such as sensitivity, temporal resolution in glutamate monitoring and potential to simultaneously determine other neurotransmitters will be reviewed and discussed. Finally, in order to give a well-balanced opinion regarding the analysis of glutamate in brain microdialysate, the high performance liquid chromatography technology will be also reviewed.