MELATONIN REDUCES H2O2-INDUCED LIPID-PEROXIDATION IN HOMOGENATES OF DIFFERENT RAT-BRAIN REGIONS

The ability of melatonin to modify H2O2-induced lipid peroxidation in brain homogenates was determined. The concentrations of brain malonald ehyde (MDA) and 4-hydroxyalkenals (4-HDA) were assayed as an index of induced membrane oxidative damage. Homogenates from five different reg ions of the brain (cerebral cortex, cerebellum, hippocampus, hypothala mus, and corpus striatum) derived from two different strains of rats, Sprague-Dawley and Wistar, were incubated with either H2O2 (5 mM) alon e or H2O2 together with melatonin at increasing concentrations ranging from 0.1 to 4 mM. The basal level of lipid peroxidation was strain-de pendent and about 100% higher in homogenates from the brain of Wistar rats than those measured in Sprague-Dawley rats. MDA + 4-HDA levels in creased after H2O2 treatment in homogenates obtained from each region of the brain in both rat strains but the sensitivity of the homogenate s from Sprague-Dawley rats was greater than that for the homogenates f rom Wistar rats (increases after H2O2 from 45 to 165% compared 20 to 4 0% for Sprague-Dawley and Wistar rats, respectively). Melatonin co-tre atment reduced H2O2-induced lipid peroxidation in brain homogenates in a concentration-dependent manner; the degree of protection against li pid peroxidation was similar in all brain regions.