Cytokinetics of neonatal cerebellar neurons in rats as studied by the ?complete H3-thymidine labelling? method

The development of rat cerebellum was studied by the complete 3H-thymidine labelling method which provides a 100% labelling of cell nuclei at the time of birth. The decrease in labelling index and intensity after birth was studied for a total of 42 days in order to compare proliferative activity of the different cell populations. The results indicate that Purkinje cells and cells of the nucleus lateralis cease to divide after birth. Golgi cells showed a very slow proliferative activity up to day 20. A rapid cell turnover rate was found for basket cells and cells of the molecular layer up to day 8 and a slow proliferation at later times. A high proliferative activity of the external granular layer cells after day 3 to day 8 and a similar decline of labelling over internal granular cells was found. The latter finding was interpreted as being due to cell renewal of internal granular cells as well as cell migration from external granular cells into the internal granular layer. The transit time for the migratory process was calculated to be approximately 24 hours.