This is a slice of the midline vermis in the cerebellum of a 60-day-old rat that was injected with 3H-thymidine on 2 consecutive days: P14 and P15.
As with the previous injection group, most cells in the MOLECULAR LAYER that are judged to be neurons are unlabeled throughout the entire cerebellum. Only a few very superficial stellate cells are found scattered about; these are the youngest stellate cells. Most labeled cells in the molecular layer are endothelial cells and glia. Unlabeled cells in the GRANULAR LAYER predominate throughout the lingula and nodulus. the majority of granule cells are unlabeled in deep parts of the centralis, culmen, declive, pyramis, centralis, and uvula. Labeled granule cells still predominate in superficial lobules of the central lobe--especially in the declive, tuber, and pyramis. All unlabeled granule cells were generated before the morning of P14. But since many more unlabeled granule cells are present compared to the P12-13 group, a fair number of granule cells were generated on P12 and P13.
Most probable composition of the external germinal layer (egl):
1. Basket cell precursors are absent.
2. Stellate cell precursors are virtually absent.
3. All of the remaining and shrinking egl is populated with granule cell precursors.