[Measurements of monoamine neurotransmitter metabolism by in vivo voltammetry]

In vivo voltammetry is an electrical detection method by which dopamine and serotonin metabolism can be estimated in the brain of animals. In the present report preliminary and basic experiment were performed before its application to ischemic brain. Firstly, using voltammetry DPV-5 system in vitro, concentration/amplitude curve was obtained with various concentration of 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) diluted in phosphate buffer (pH 7.4). DOPAC appeared at +150 mV (peak 2) while 5-HIAA appeared at +300 mV (peak 3). A linear relation was obtained in the concentrations ranging 5 x 10(-6)-10(-4) M for DOPAC and 10(-6)-10(-4) M for 5-HIAA. While a delay in oxidation potential was noticed for both peaks 2 and 3 by about 30 mV when the pH of solution was decreased by 1. Secondly the DPV-5 system was applied in vivo to the rat striatum. Peak 2 was observed at +150 mV which was increased by intraperitoneal injection of haloperidol, a dopamine receptor blocker and decreased by pargyline, a monoamine oxidase inhibitor. While peak 3 was observed at +300 mV and increased after probenecid and decreased by pargyline, which suggest that peak 2 and 3 correspond to DOPAC and 5-HIAA respectively. Thirdly DPV-5 system was applied to the rat striatum and rat's heart was arrested by KCl injection as a model of extreme brain ischemia. Shortly after cardiac arrest the heights of peak 2 was significantly increased to 600-900% while the increase of peak 3 was not significant, both of which subsided gradually toward 30 minutes after arrest.(ABSTRACT TRUNCATED AT 250 WORDS)