Spatial and temporal pattern of postnatal proliferation of Bergmann glial cells in rat cerebellum: an autoradiographic study.

In order to examine the relationship between the Bergmann glial cells and the migrating granule cells, the development of the Bergmann glial cells in the rat cerebellum was studied with 3H-thymidine autoradiography. 3H-thymidine was injected intraperitoneally into rats on two days successively between days 2 and 21 of the postnatal age (PD2 and PD21). All animals were sacrificed on PD25 and the vermis of the cerebellum was embedded in epoxy resin. Semithin sections were cut sagittally for autoradiography. The labeling index of the Bergmann glial cells in lobules I, II, III, IV, V, VIa, VIII, IX, and X reached the peak on PD6-7, and in lobules VIb and VII on PD8-9. Moreover, the lobules could be divided into three groups according to the day when cumulative labeling indices reached 50% of the total ones (LI50): The early-developing group (LI50; PD4.4-5.2) contained lobules I, II, III, IV, and V, the intermediate group (LI50; PD5.3-6.1) lobules VIa, VIII, IX, and X, and the late-developing group (LI50; PD6.6-7.8) lobules VIb and VII. The regional gradient of LI50 in the Bergmann glial cells corresponded approximately to the regional gradient in the ratio of late-forming granule cells; that is, the later the LI50 of the Bergmann glial cells, the higher is the ratio of the late-forming granule cells. This suggests that an intimate relationship exists between these two kinds of cells.