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

The effect of L-3,4-dihydroxyphenylalanine (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.mu l(-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 mu l.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). (C) 1996 Elsevier Science Ireland Ltd.