Antioxidant Effects of Serotonin and L-DOPA on Oxidative Damages of Brain Synaptosomes

Antioxidant Effects of Serotonin and L-DOPA on Oxidative Damages of Brain Synaptosomes

<P> Antioxidant effects of serotonin and L-DOPA on neuronal tissues were examined by studying the oxidative damages of brain synaptosomal components. The study further explored the mechanism by which they exert protective actions. Serotonin and L-DOPA (1 μM to 1 mM) significantly inhibited lipid peroxidation of brain tissues by either Fe<SUP>2&#8290;</SUP> and ascorbate or t-butyl hydroperoxide in a dose dependent fashion. Protective effect of serotonin on the peroxidative actions of both systems was greater than that of L-DOPA. Protein oxidation of synaptosomes caused by Fe<SUP>2&#8290;</SUP> and ascorbate was attenuated by serotonin and L-DOPA. Protein oxidation more sensitively responded to L-DOPA rather than serotonin. Serotonin and L-DOPA (100 μM) decreased effectively the oxidation of synaptosomal sulfhydryl groups caused by Fe<SUP>2&#8290;</SUP> and ascorbate. The production of hydroxyl radical caused by either Fe<SUP>3&#8290;</SUP>, EDTA, H<SUB>2</SUB>O<SUB>2</SUB> and ascorbate or xanthine and xanthine oxidase was significantly decreased by serotonin and L-DOPA (1 mM). Equal concentrations of serotonin and L-DOPA restored synaptosomal Ca<SUP>2&#8290;</SUP> uptake decreased by Fe<SUP>2&#8290;</SUP> and ascorbate, which is responsible for SOD and catalase. Protective effects of serotonin and L-DOPA on brain synaptosomes may be attributed to their removing action on reactive oxidants, hydroxyl radicals and probably iron-oxygen complex, without chelating action on iron.