Ionizing radiation-induced apoptosis of proliferating stem cells in the dentate gyrus of the adult rat hippocampus.

The occurrence of radiation-induced apoptosis in normal brain was investigated using an animal model of radiosurgery. Adult male Fischer rats aged 3 to 4 months were subjected to single dose convergent beam irradiation (10 Gy). Apoptotic cell death was determined by in situ labeling of DNA nick ends (TUNEL) and light microscopic evaluation of cell morphology. Five hours after irradiation, a highly significant increase of apoptotic cells in the subgranular zone of the dentate gyrus was paralleled by a corresponding significant decrease of cells immunoreactive for the proliferation marker Ki-67. Morphology, location and distribution of cells affected by radiation-induced apoptosis in the dentate gyrus subgranular zone, together with NeuN-immunohistochemistry, support the contention that these cells belong to the immature progenitor population responsible for neurogenesis in the adult rat hippocampus. Copyright 1999 Published by Elsevier Science B.V.