The effect of brominated flame retardants on neurotransmitter uptake into rat brain synaptosomes and vesicles

The environmental levels of brominated flame retardants (BFRs) are increasing, but little is known about their toxic effects. In this paper, we show that some of the most important BFRs in commercial use today, have a neurotoxicological potential. Hexabromocyclododecane (HBCD) and tetrabromobisphenol-A (TBBPA) inhibit plasma membrane uptake of the neurotransmitters dopamine, glutamate and gamma-amino-n-butyric acid (GABA) at a concentration level similar to what previously found for polychlorinated biphenyls (PCBS) and even for ecstasy. The IC50 value for HBCD on dopamine uptake was 4 muM, and the IC50 values for TBBPA were 9, 6 and 16 muM for dopamine, glutamate and GABA, respectively. HBCD also inhibited glutamate uptake at low concentrations, but never achieved more than 50% inhibition. The inhibition was primarily due to their effect on the membrane potential, measured by the membrane potential marker tetrapherylphosphonium. bromide (TPP+). Other brominated flame retardants such as octaBDE and decaBDE did not have any effects on uptake. TBBPA, HBCD and even the pentabrominated diphenylether mixture (pentaBDE, DE-71, Great Lakes) also inhibited the vesicular uptake of dopamine with an IC50 value of 3, 3 and 8 muM, respectively. The neurotoxicological consequences of these findings for environmental contaminants such as BFRs and PCBs are discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.