In utero exposure to low-doses of ionizing radiation decelerates neuronal migration in the developing rat brain.

In order to elucidate the possible mechanisms for the effects of low doses of ionizing radiation on the developing rat cerebral cortex we studied how neuronal migration can be affected by prenatal in utero irradiation. We have demonstrated an effect of ionizing radiation on neuronal migration at doses as low as 15 cGy together with a changing pattern of expression of the neural cell adhesion molecule N-CAM. After a dose of 15 cGy or more there was a reduction in N-CAM immunoreactivity in the matrix cell zone which became apparent about 24 h after exposure and continued until 48 h after exposure. Normal reactivity occurred 3 days after exposure to radiation. However, there was no obvious change in the immunoreactivity for L1, MAP2, tau protein or neurofilament. Our findings suggest the possible role of N-CAM in neuronal migration and also suggest the presence of a threshold in terms of the effects of small radiation doses on the developing cerebral cortex.