Differential pulse voltammetry in vivo--evidence that uric acid contributes to the indole oxidation peak

Previous studies using differential pulse voltammetry have shown that indoleamines contribute to the oxidation peak at +280-300 mV (peak 3) measured in the rat striatum in vivo using carbon fibre electrodes. In this study, using similar techniques, it is shown that 5-hydroxyindoleacetic acid and uric acid oxidize at a similar potential (+270-290 mV) in vitro. Additionally, by microinfusing uric acid or its metabolizing enzyme uricase, it is shown that uric acid oxidation contributes to about 30% of the height of peak 3 measured in the rat striatum in vivo. These results indicate that care needs to be taken in interpreting changes in the height of the in vivo peak 3 since it is not solely due to the oxidation of brain indoleamines.