[en] Objective: To identify the cell death type and investigate the potential mechanism of ionizing radiation-induced neural cell death in the neonatal rat cerebral cortex. Methods: The neonatal Wistar rats were given a single dose of 2.0 Gy γ-irradiation. The cell death type and characterization in cerebral cortex were identified using DNA electrophoresis, TUNEL and HE staining. The P53- and iNOS-positive cells were analyzed quantitatively using imnmnohistochemistry. Results: The DNA and morphological characterization of death cells indicated that 2.0 Gy γ-irradiation induced apoptosis of the neural cells in neonatal rat cerebral cortex. The apoptosis indices in different cortex regions were significantly increased 4 h after irradiation, and reached the peak value at 12 h post-irradiation. The apoptosis index of neocortex was much higher than that of hippocampus (archicortex) and paleocortex, while paleocortex had lower apoptosis index than hippocampus. The quantitative immunohistochemistry suggested that the numbers of P53 and iNOS-positive cells were not different between these three cortex regions at the same time-point after irradiation. Conclusion: 2.0 Gy γ-rays induced apoptosis of the neural cells in neonatal rat cerebral cortex. The response of cells to the damage effects of ionizing radiation was similar in different cortex regions; however, the apoptosis indices were different significantly. These findings imply that the developing phase or type of neural cells may play a pivotal role in the apoptosis process induced by ionizing radiation. (authors)