Monitoring of dopamine metabolism by in vivo voltammetry and high performance liquid chromatography in L-dopa-treated rats.

Following L-DOPA administration, DA metabolites were measured by both in vivo voltammetry and HPLC-ECD. In vivo, the amplitudes of the catechol oxidation currents in both the striatum and frontal cortex increased and reached a plateau from 60 min to 240 min after L-DOPA treatment. L-DOPA, DA, DOPAC and HVA levels measured by HPLC-ECD after L-DOPA treatment were increased in both regions, and the occurrence of the peak of each compound was dependent on its order in the metabolic pathway, i.e., 15 min for DA, 45 min for DOPAC and 60-180 min for HVA. However, NE remained unchanged. No indication of a rapid DA increase was apparent in the catechol oxidation current at 15 min; and thus, DA is unlikely to be a main contributor to the catechol oxidation current in the brain of rats treated with L-DOPA.