Intracranial microdialysis of salicyclic acid to detect hydroxyl radical generation by monoamine oxidase inhibitor in the rat

Abstract

The effect of pargyline, a monoamine oxidase inhibitor, on the generation of hydroxyl free radicals ( .OH) was investigated using striatal microdialysis. Salicylic acid in Ringer's solution (0.5 nmol μl −1 min −1) was infused through a microdialysis probe to detect the generation of hydroxyl radicals ( .OH) as reflected by the formation of dihydroxybenzoic acid (DHBA) in the striatum. When pargyline (100 nmol μl −1 min −1) was infused in rat brain, the level of 3,4-dihydroxyphenylacetic acid (DOPAC) gradually decreased in a time-dependent manner. In addition, a marked elevation of DHBA was observed. The present results indicate that accumulation of dopamine (DA) in the extracellular fluid elicited by pargyline can be auto-oxidized, which in turn leads (possibly by an indirect mechanism) to the formation of cytotoxic .OH free radicals.