Evaluation of the effect of chronic exposure to 137Cesium on sleep-wake cycle in rats.

Abstract Since the Chernobyl accident, the most significant problem for the population living in the contaminated areas is chronic exposure by ingestion of radionuclides, notably 137 Cs, a radioactive isotope of cesium. It can be found in the whole body, including the central nervous system. The present study aimed to assess the effect of 137 Cs on the central nervous system and notably on open-field activity and the electroencephalographic pattern. Rats were exposed up to 90 days to drinking water contaminated with 137 Cs at a dosage of 400 Bq kg −1 , which is similar to that ingested by the population living in contaminated territories. At this level of exposure, no significant effect was observed on open-field activity. On the other hand, at 30 days exposure, 137 Cs decreased the number of episodes of wakefulness and slow wave sleep and increased the mean duration of these stages. At 90 days exposure, the power of 0.5–4 Hz band of 137 Cs-exposed rats was increased in comparison with controls. These electrophysiological changes may be due to a regional 137 Cs accumulation in the brain stem. In conclusion, the neurocognitive effects of 137 Cs need further evaluation and central disorders of population living in contaminated territories must be considered.