Uranium is an environmental ubiquitous metal-trace element. It has both chemical and radiological toxicity. After chronic ingestion, uranium can distribute in any part of the body and accumulate in the brain. The aims of this study was i) to determine and estimate the effects of uranium on dopaminergic serotoninergic and cholinergic systems and ii) to measure the uranium amount in the brain, after chronic exposure by ingestion of depleted (DO) or enriched (EU) uranium g 1.5 to 18 months at 40 mg.l-1 (40 ppm) in different rat brain areas. At any time time of exposure, the results show that both neurotransmission alterations and the uranium brain accumulation were moderate, area-specific, time-evoluted and depended on uranium specific activity. After DU exposure, monoamine perturbations are chronic and progressive. ON the contrary, monoamine alterations occured only after long term of EU exposure. These monoaminergic modifications are not always dependent on uranium accumulation in brain aeras. Moreover, although the cholinergic system was not affected at both 1.5 and 9 months of DU exposure, the alteration of ChE activity after EU exposure are both dependent on uranium accumulation in brain aeras and on uranium specific activity. After EU exposure, cholinergic modification and uranium accumulation in hippocampus could partially explain the short-term memory disturbances wich have been previously reported.
Key words: uranium; brain; central nervous system; chronic contamination; contamination by ingestion; dopaminergic system; serotoninergic system; cholinergic system; toxicity; neurotoxicity; chemical toxicity; radiological toxicity;