Real-Time Measurements of Phasic Changes in Extracellular Dopamine Concentration in Freely Moving Rats by Fast-Scan Cyclic Voltammetry - Drugs of Abuse: Neurological Reviews and Protocols - page 435

Fig. 1. Voltammetric signals. The input waveform (A) is applied to the carbon
fi ber microelectrode which produces a background output current (B) . There are two
background signals superimposed, one prior to and one after an electrical stimulation
that evoked dopamine release. Because the background current is stable, the signals
superimpose well. However, when there is oxidation of dopamine or reduction of
dopamine- o -quinone (peak reaction times represented by the dashed vertical lines ),
there are slight deviations of the signals due to faradaic current. If the prestimulation
background signal is subtracted from the post-stimulation signal, the faradaic current is
revealed (C) . Note from the scales of the y -axes that the faradaic current for dopamine
oxidation is <1% of the background current despite this being a relatively large
biologically signal (~1 M ). The background-subtracted signal can be plotted against

the applied potential to give a cyclic voltammogram (D) . This is the analytical tool
for chemical resolution with fast-scan cyclic voltammetry. The current at the peak
oxidation potential for dopamine from multiple scans can be plotted against time to
reveal the temporal profi le of dopamine (E) . Each point represents current from one
voltammetric scan, collected every 100 ms. Note that the current in this graph is plotted
negative up so that an increase in dopamine is represented by an upward defl ection.
The signal shown is dopamine release in the caudate-putamen of a freely moving
rat evoked by an electrical stimulation (24 pulses, 60 Hz, ±120

µ

µ A, 2 ms/phase)

represented by the bar .