The effects of castration on the subependymal plate of the rat.

Earlier studies have shown that glial tumours, produced by the intracerebral implantation of chemical carcinogens, originate from the subependymal plate. In the present study the effects of castration on cell number and proliferation in the subependymal region has been investigated as such treatment has been shown to reduce the incidence of gliomata produced by an implanted carcinogen. An age-related reduction in mitotic activity and nuclear density was found in the subependymal plate. Castration produced a consistent reduction in mitotic activity but the nuclear density was unchanged. The results suggest that the reduction in tumour incidence produced by castration cannot be explained simply on the basis of reduced proliferation in the population believed to be at risk and that other, as yet, undefined factors must be involved. In addition, it appeared that there was also no simple relationship between brain growth and cell proliferation in the subependymal plate.