Gliogenesis and ependymogenesis during embryonic development of the rat. An autoradiographic study

With the aid of [3H]thymidine autoradiography gliogenesis and ependymogenesis were studied in the brain of the rat during embryonic development. Gliogenesis was found to begin on day 17 of gestation in the caudal regions of the brain stem, and to spread rostrally. On days 20 and 21 of gestation gliogenesis reached a peak, and then declined. Ependymogenesis began earlier and showed the following pattern: day 14 of gestation in the 4th ventricle and cerebral aqueduct, day 15 in the 3rd ventricle, and day 17 in the lateral ventricles reaching a peak on different days in different sites. Both gliogenesis and ependymogensis continued up to the last day of gestation, day 22. Issues pertaining to gliogenesis and the formation of glioblasts, and the relationship between gliogenesis and ependymogenesis are discussed.