Microdialysis methods have been widely used for the quantitative measurement of neurotransmitter concentrations in vivo. Because neurotransmitter efflux happens rapidly, microdialysis has a limit to detect neurochemical changes in the brain in real time. Fast-scan cyclic voltammetry (FSCV) is one of the electroanalytical methods to monitor neurotransmitter efflux such as dopamine, serotonin, adenosine, and ascorbic acid in the brain. Because conventional FSCV analyzes voltammagram differences to detect chemical substances, measuring concentrations of neurotransmitters is desirable. In a previous study we introduced a new method using multi-waveform cyclic voltammetry to reduce voltammogram differences and enhance sensitivity and selectivity.

In this study, we demonstrated FSCV with a carbon fiber microelectrode (CFM) adjacent to a microdialysis probe to measure concentration changes during microdialysis. Experiments were performed in agarose gel (0.1%) with a known concentration of dopamine inside, and perfusion of the dialysis probe with Tris-buffered saline (TBS, pH7.4, 5ul/min) decreased the baseline. After stabilization, a series of known concentrations of dopamine (200nM to 1uM) was perfused and concentration changes were monitored by FSCV until the decreased baseline was recovered. These results indicate that the amount of dopamine injected when decrease baseline is fully recovered reflects the concentration of dopamine inside the agarose gel. FSCV combined with microdialysis was also performed in the striatum of a rat, to monitor basal level of dopamine in the extracellular space of the brain.