Dopamine but not 3,4-dihydroxy phenylacetic acid (DOPAC) inhibits brain respiratory chain activity by autoxidation and mitochondria catalyzed oxidation to quinone products: Implications in Parkinson's disease

This study reveals that, in contrast to dopamine (DA), 3,4 dihydroxyphenylacetic acid (DOPAC) during in vitro incubation up to 2 h causes only marginal inhibition of rat brain mitochondrial respiratory chain activity, a minimal loss of protein free thiols and very little quinoprotein adduct formation. The damaging effects of DA on brain mitochondria are, however, conspicuous and apparently mediated by quinone oxidation products generated by autoxidation of DA as well as catalyzed by a mitochondrial activity, inhibitable by clorgyline (2.5-10 μM) and cyanide (1 mM).