Comparison of the effects of enriched uranium and 137-cesium on the behaviour of rats after chronic exposure

Purpose: A radionuclide that accumulates in the central nervous system is likely to exert both a chemical and a radiological effect. The present study aimed at assessing the behavioral effect of two radionuclides previously shown to accumulate in the central nervous system after chronic exposure – uranium and cesium.

Materials and methods: Rats were exposed for 9 months to drinking water contaminated with either enriched uranium at a dosage of 40 mg U · l−1 or 137-cesium at a dosage of 6500 Bq · l−1, which correspond to the highest concentrations measured in some wells in the south of Finland (uranium) or in the milk in Belarus in the year following the Chernobyl accident (137-cesium).

Results: At this level of exposure, 137-cesium had no effect on the locomotor activity measured in an open-field, on immobility time in a forced swimming test, on spontaneous alternation in a Y-maze and on novel object exploration in an object recognition test. Enriched uranium exposure specifically reduced the spontaneous alternation measured in the Y-maze after 3 and 9 months exposure although it did not affect the other parameters.

Conclusion: Enriched uranium exposure altered the spatial working memory capacities and this effect was correlated with previously described accumulation of uranium in the hippocampus which is one of the cerebral areas involved in this memory system.