Dopa and 3- O-methyldopa in cerebrospinal fluid of parkinsonism patients during treatment with oral l-dopa

Abstract

In a study of dopa metabolism as reflected in the cerebrospinal fluid of parkinsonism patients during l-dopa therapy, it became evident that 3- O-methyldopa is present in these fluids in a concentration eight to ten times that of dopa. This concentration is sufficiently high to cause significant interference in the determination of dopa if appropriate corrections are not made. New fluorimetric methods for the determination of 3- O-methyldopa and dopa in cerebrospinal fluid were devised. The procedure for determination of dopa has the advantage of greater sensitivity than the traditional iodine oxidation method. A thin-layer chromatographic search was made for the metabolites of 3- O-methyldopa, vanilpyruvic acid and vanillactic acid, in cerebrospinal fluid. Neither was found, suggesting that the 3- O-methyldopa in cerebrospinal fluid originates largely from systemic metabolism of dopa rather than from the central nervous system. These findings are discussed in the light of present trends in l-dopa therapy.