EFFECT OF A CATECHOL-O-METHYL TRANSFERASE INHIBITOR, U-0521, WITH LEVODOPA ADMINISTRATION

The in vivo effect of 3,4-dihydroxy-2-methyl-propriophenone (U-0521) was studied in rats treated with l-Dopa, 250 mg/kg, intraperitoneally. In a time-course study, experimental animals received two doses of U-0521, 250 mg/kg, i.p., 30 min before l-Dopa and along with l-Dopa. Rats were decapitated at intervals of 30-120 min. U-0521-treated animals showed elevated levels of plasma and brain DOPA and of brain dopamine; they also had a reduction of 3-O-methyldopa (OMD) in plasma and brain, and of homovanillic acid (HVA) in brain, compared to rats treated with l-Dopa alone. A dose-response study of U-0521, given 30 min before l-Dopa, showed that there was effective inhibition of plasma and brain OMD accumulation at a dose of U-0521 of 100 mg/kg, i.p., or greater. Brain HVA accumulation was inhibited at a dose of 200 mg/kg, i.p., or greater. U-0521 can effectively block formation of O-methylated metabolites of l-DOPA and dopamine peripherally and centrally after high dosage l-Dopa administration. © 1979.