PEROXIDATION OF SYNAPTOSOMES ALTERS THE DOPAMINE UPTAKE COMPLEX BUT SPARES THE EXOCYTOTIC RELEASE OF DOPAMINE

Synaptosomes, prepared from the striata of mice, and incubated for 1 h in a Krebs-Ringer medium with the peroxidative combination of ascorbi c acid (0.1 mM)/Fe2+ (1 mu M), lose their ability to take up [H-3] dop amine. This effect is associated with a decrease in binding of the dop amine uptake inhibitor [H-3] GBR 12783. The free radical scavenger tro lox C (0.1 mM) and the Ginkgo biloba extract EGb 761 (10 mu g/ml) prev ent both effects. Although submitted to these peroxidative conditions after loading with [H-3] DA, superfused synaptosomes retain their abil ity to release [H-3] DA when depolarized by high potassium concentrati ons (40 mM). This release is higher than that observed when synaptosom es are incubated without ascorbic acid/Fe2+, and does not seem to depe nd upon peroxidation, since it is also observed when incubation is per formed in the presence of the free radical scavengers EGb 761 (10 mu g /ml) and trolox C (0.1 mM).