Radiation induced damage in the choroid plexus of the rat brain: a histological evaluation

Early and late histological changes have been investigated in the choroid plexus after the local irradiation of the brain of rats with single doses of 17 X 5-25 Gy of X-rays. Changes were seen in epithelial cells within 1 week of irradiation. This was characterized by vacuolation, blebbing and partial lysis of the cytoplasm. Oedema in the underlying connective tissue was also seen after 1 week. A marked reduction in the number of endothelial cells, lining the walls of blood vessels, was found after 12 weeks; the severity was dose related and increased with time after irradiation. Slight atrophy of the epithelium was seen after 12 weeks. The reduction in endothelial cell number was associated with an attempt at regeneration as indicated by endothelial nuclear enlargement, nuclear pairs or groups and by the appearance of mitotic figures. Evidence or epithelial regeneration was not seen until week 26. Interstitial fibrosis was seen from 26 weeks after irradiation with the severity being both dose and time related. These late fibrotic changes were associated with basal membrane thickening, degenerative changes in the tunica media of arterioles and the appearance of thrombi. These changes are compared and contrasted with those seen in other normal tissues after irradiation and are discussed in terms of their relevance to the development of late radiation damage to the central nervous system.