The brains of normal and irradiated C57BL/J6 adult female mice were studied for morphologic and biochemical differences at four and six hours after focal brain irradiation when the animals first experienced seizures and, at the terminal phase just prior to death. Focal irradiation of the brain was performed under stereotaxic conditions with microbeams delivered through a 5.0 × 9.0 mm aperture to the dorsal surface of the brain at an adsorbed surface dose of 50,000 rad.
An analysis of variance did not indicate any difference in brain weight or in DNA, RNA, or protein concentration due to irradiation. There was a significant increase in 5-HT and NE concentration, and in AChE activity in the brains of the irradiated groups. Histochemical observations failed to show differences in the localization of alkaline and acid phosphatase activity. However, localization of ATPase activity associated with the blood vessels was more diffuse in the irradiated regions of the brain. Biochemical comparisons of ATPase activity indicated that there was a change in the subcellular distribution of ATPase enzyme following irradiation. Light and electron microscopic comparisons revealed a selective damage to astrocytes and dendritic processes in irradiated regions of the cortex.