Protective effect of carbidopa on hydroxyl radical generation in the rat striatum by dopamine

Abstract

The effect of l-3,4-dihydroxyphenylamine ( l-DOPA) on the generation of hydroxyl free radicals (·OH) was investigated using striatal microdialysis technique. Salicylic acid in Ringer's solution (0.5 nmol. μl −1.min −1) was infused directly through a microdialysis probe to detect the generation of ·OH as reflected by the formation of dihydroxybenzoic acids (DHBA) in the striatum. When l-DOPA (0.1 mM; 1 μl.min −1) was infused in the rat brain, the level of 3,4-dihydroxyphenylacetic acid (DOPAC) gradually increased in a time-dependent manner. In addition, a marked elevation of DHBA was observed. However, in the presence of carbidopa, a decarboxylase inhibitor, the elevation in DHBA formation was not observed. These results suggest that carbidopa may suppress the ·OH generation by dopamine (DA).