DIFFERENTIAL RADIOSENSITIVITY OF MOUSE EMBRYONIC NEURONS AND GLIA IN CELL CULTURE

The responses of neurons and glial cells to ultraviolet and γ-radiation were studied in cell cultures of embryonic mouse brains. A decrease in the ratio of glia to neurons occurred after both forms of irradiation. [H]thymidine labelling followed by autoradiography revealed that all glia were capable of replication, whereas 70% of neurons were non-replicating under the conditions of the study. Ultraviolet radiation caused a decrease in the proportion of replicating neurons but did not affect the proportion of replicating glia, whereas γ-radiation caused a decrease in DNA replication in both cell types. Levels of ultraviolet radiation-induced unscheduled DNA synthesis were lower in neurons than in glia. It is concluded that sensitivity to both ionizing and ultraviolet radiation of neurons and glial cells in embryonic brain cultures is determined primarily by the capacity for and state of DNA replication. Neurons which have already reached the stage of terminal differentiation are more resistant than replicating neurons of glial cells.