A quantitative study of cell proliferation in ependyma and choroid plexus in the postnatal rat brain

Profliferative activity in forebrain ependyma aand choroid plexus epithelium was studied in rats aged up to 42 days by means of autoradiography after injection of [3H]-thymidine. Labelling indices were higher in the lateral than in the third ventricle, while values for choroid plexus epithelium were lower than those for ependyma. In all areas examined, labelling indices showed a similar pattern of decline in the first two postnatal weeks reaching by day 12 a level about 20-30% of that on day 1. This low level, corresponding to a turnover time of 130 days for ependyma, was maintained tereafter up to day 42, indicating the persistence of proliferation in the young adult.