In vivo temporal sequence of rat striatal glutamate, aspartate and dopamine efflux during apomorphine, nomifensine, NMDA and PDC in situ administration.

In vivo microdialysis was used to investigate the interactions between dopamine (DA), glutamate (Glu) and aspartate (Asp) in anaesthetised-rat striatum. The combination of brain microdialysis and capillary electrophoresis with laser-induced fluorescence detection (CE-LIFD) allows the simultaneous monitoring of the efflux of these neurotransmitters up to every 10 s. DA and Glu reuptake inhibitors, nomifensine and L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) and, dopaminergic and glutamatergic receptor agonists, apomorphine and NMDA respectively, were administered by reverse dialysis. Reverse dialysis of 20 micro M nomifensine induced a rapid and marked increase (+3200% at 5 min) in extracellular DA, while a decrease in Glu and Asp (-11 and -25%, respectively) was observed simultaneously. Reverse dialysis of 10 micro M apomorphine led to progressive changes: -63% decrease in DA and +25% Glu increase at 36 min. Reverse dialysis of 1 mM NMDA induced a simultaneous increase in DA, Glu and Asp which peaked at +2 min (+840%, +40% and +150%, respectively). Surprisingly, a second increase in Glu was observed 5 min after the end of NMDA perfusion. Reverse dialysis of PDC (1 mM and 10 mM) induced a rapid increase in Glu and Asp levels, while DA increased with a 26-s delay. These findings indicate that, in the striatum, endogenous DA and Glu may act in opposition to regulate each other's efflux. These results have been obtained due to unique features offered by microdialysis coupled with CE-LIFD.