Enriched uranium affects cognitive behaviour and the sleep cycle to a greater extent than depleted uranium sources
Uranium has numerous effects at cognitive level. Our experimental studies in the rat have shown a reduction of 10 to 20% in short-term memory following chronic contamination with 4% enriched uranium (EU) for 1.5 and 9 months (2 mg/kg/day via drinking water) (Houpert et al., 2005; Houpert et al., 2007) as shown in Figure 1. Conversely, the same contamination protocol carried out with depleted uranium (DU) was devoid of significant effect (Houpert et al., 2005). Other studies have shown that the learning processes of the location of an immersed platform (Morris water test) seem reduced following chronic ingestion of DU but at concentrations higher than those used in our experiments (10, 20 or 40 mg/kg/day, 3 months and 80 mg/kg, 4 weeks) (Albina et al., 2005).
We have also shown a disorder in the wake-sleep cycle following the ingestion of EU (2 mg/kg/day via drinking water). However, this was not observed with DU. In fact, an increase in the quantity of paradoxal sleep following sub-chronic contamination of 1 and 2 months’ duration were observed (+47% and +66%, respectively). This increase disappeared when contamination was extended to 3 months (Lestaevel et al., 2005). This result suggests an adaptive response. Moreover, the anxiety of rats is increased after 1.5 months’ contamination with EU whereas contamination with DU has no effect (Houpert et al., 2005). Together, these results highlight the importance of the radiological toxicity of uranium.