Spontaneous DNA breaks in the rat brain during development and aging.

The level of spontaneous DNA breaks in nuclei isolated from the cerebral cortex of rat embryos at 12, 15 and 19 days of gestation, and from cerebral cortex and cerebellum of 24-day-, 6-month- and 36-month-old rats was measured by alkaline elution. A constant low level of DNA breaks was found in brain DNA during development from an embryo at day 12 of gestation to a 24-day-old rat. During aging the level of DNA breaks remained at the same low level, as shown by comparing nuclei from the cerebral cortex and cerebellum of 6- and 36-month-old animals. By contrast, an almost 2-fold increase in the level of DNA breaks was observed in rat liver nuclei between 6 and 36 months of age, confirming our earlier findings on isolated liver cells. Although there were no changes in the level of DNA breaks in rat brain during development or during aging, breaks accumulated rapidly post mortem. The rate of this process was not age-dependent. Our data suggest that the level of spontaneous DNA breaks in the brain is not likely to be of fundamental importance in the complex cellular alterations associated with brain development and aging.