Multi-waveform fast-scan cyclic voltammetry mapping of adsorption/desorption kinetics of biogenic amines and their metabolites†
Fast-scan cyclic voltammetry (FSCV) is an effective method for investigating electro-active neurochemical species. In recent years, FSCV has been used to measure electro-active neurotransmitters in a variety of neuroscience studies. We previously reported on the use of paired-pulse voltammetry (PPV) that enables FSCV to differentiate various analytes and minimize confounding factors by taking advantage of the adsorption characteristics of the analyte on carbon fiber microelectrodes. In spite of a number of studies regarding adsorption/desorption characteristics of neurotransmitters, the difference in adsorption/desorption properties among neurotransmitters has yet to be fully explored. To calculate adsorption/desorption constants for neurotransmitters, we propose the use of multi-waveform FSCV (M-FSCV), which consists of ten triangular waveforms in a single scan. Within the multiple waveforms, the voltammetric response of dopamine decayed exponentially because of the decreased adsorption time period. The decay pattern was mathematically described using adsorption/desorption characteristics and two additional initial points: an exponential decay constant (K) and an initial quantity (A), which were extracted from the decay equation. Using this method, we were able to quantify the decay constant (K-map) and an initial quantity (A-map) color plot in addition to a conventional pseudo color plot. M-FSCV was evaluated with two biogenic amine groups (catecholamines and indolamines) to characterize their inherent adsorption/desorption constants. As a result, the A-map showed a high correlation with concentration and the K-map for each group to be significantly differentiated. These results demonstrate that M-FSCV has the potential to be a useful technique for acquiring additional adsorption/desorption information regarding neurotransmitters.