Comparative Radiosensitivity of Developing Brain Structures in the Rat After Gamma Irradiation

Purpose: To compare the radiosensitivities of proliferative layers of the olfactory bulb (OB), the dentate gyrus of the hippocampus (DG) and the cerebellum (C)

Status: 1990 - 1992, terminated

Treatment: Single whole body gamma irradiation with doses from 0.1 to 12 Gy (dose rate 0.19 Gy/min) from a Co-60 gamma source irradiation. Animals sacrificed and brains removed 3, 6 or 9 h after exposure

Dosimetry: Ionization chamber

Endpoints: Quantification of radiation-induced apoptosis in semi-thin sections, development with time of radiation-induced lesions, cell survival curves

Animal: Sprague-Dawley CFA albino rats at an age of 14 days, sham irradiated and irradiated rats randomly chosen.

Results: Irradiated injured cells in the central nervous system develop a typical apoptotic appearance. The number of apoptotic cells incrases dramatically with time 5 hours after exposure. The survival rate of immature granule cells was evaluated in function of the dose. In both, the olfactory bulb and the dentate gyrus, the dose-effect relationship was complex. In the cerebellum, this relationship followed a negative exponential function. These results suggest that, in the olfactory bulb and the dentate gyrus, the proliferative layer consists of two cell populations with different radiosensitivities whereas in the cerebellum only one homogeneous population is present.