[The effects of dopamine D-1 and D-2 receptor antagonists on 3,4-dihydroxyphenylacetic acid (DOPAC) in rat striatum with differential normal pulse voltammetry].

Dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) was detected by differential normal pulse voltammetry (DNPV) in chloral hydrate anesthetized rat striatum. The effects of some dopamine D-1 and D-2 antagonists on DOPAC concentration were observed in order to demonstrate the role of presynaptic D-1 and D-2 receptors in the feedback of dopamine synthesis and metabolism. The results showed that the mixed antagonists haloperidol (0.5 mg/kg s.c.) and chlorpromazine (5 mg/kg s.c.), the selective D-1 antagonist SCH23390 (1 mg/kg s.c.), and the selective D-2 antagonist sulpiride (5 mg/kg s.c.) all increased DOPAC concentration significantly. The percentages of increase were 140%, 102%, 26% and 40% in comparison with basal DOPAC concentration (14 +/- 2 mumol/L), respectively. These results indicate that not only presynaptic D-2 receptor regulates DA synthesis and metabolism, but that the presynaptic D-1 receptor also takes part in this feedback mechanism.