GINKGO-BILOBA EXTRACT EGB-761 OR TROLOX-C PREVENT THE ASCORBIC ACID FE2+ INDUCED DECREASE IN SYNAPTOSOMAL MEMBRANE FLUIDITY/

The ability of synaptosomes, prepared from striata, to take up H-3-dop amine declined rapidly during incubation at 37-degrees-C, in an oxygen ated Krebs-Ringer medium with 0.1 mM ascorbic acid. Ascorbic acid was responsible for this decrease. Its effectiveness after a 60 min incuba tion was concentration dependent from 1 muM and virtually complete for 0.1 mM. Furthermore, a decrease of synaptosomal membrane fluidity was revealed by measurements of fluorescence polarization using 1,6-diphe nyl-1,3,5-hexatriene. This decrease was potentiated by Fe2+ ions (1 mu M). In contrast, it was prevented by the Fe2+ ion chelator, desferriox amine (0.1 mM), by the Ginkgo biloba extract EGb 761 [2-16 mug/ml], as well as by the flavonoid quercetin (0.1 muM). This preventive effect was shared by trolox C (from 0.1 mM). It is concluded that peroxidatio n of neuronal membrane lipids induced by ascorbic acid/Fe2+ is associa ted with a decrease in membrane fluidity which, in turn, reduces the a bility of the dopamine transporter to take up dopamine.