Abstract
Epidemiological studies on atomic bomb survivors exposed in utero have revealed that radiation causes abnormalities of brain development. Several studies of mice and rats have also shown that prenatal irradiation of low-LET radiation induces developmental anomaly of the brain. However, little is known about the effect of prenatal irradiation on the behavior pattern in the adulthood. Therefore, we investigated the effects of neutron exposure in utero on the postnatal behavior pattern of mice. B6C3F1 mice were exposed to cyclotron-derived fast neutrons with peak energy of 10 MeV (0.02-0.2 Gy) or Cs-137 gamma-rays (0.2-1.5 Gy) on gestation day 13.5. At 6.5-8 months of age, male offsprings were examined for their neurobehavior (RotaRod, locomotor activity, forced swimming). The brains were weighed, and examined histopathologically. Control group and neutron-irradiated groups were analyzed for accumulation of radiolabeled drugs to muscarinic acethylcholine receptor and serotonin receptor by tracer method. The results obtained were as follows; (1) the brain weights decreased in dose-dependent manner in both types of radiation, (2) locomotor activity during dark period and immobility time of forced swimming increased in 0.02Gy neutron-irradiated group. Further binding of drug to each receptor in vivo was increased in 0.02Gy neutron group. In conclusion, a certain 'low dose window' exists for radiation-induced changes in neurobehavior and binding to neurotransmitter receptors.
