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: P10 and P11.
Most cells in the MOLECULAR LAYER are unlabeled throughout the entire cerebellum. These are basket and stellate cells that were generated before P10. Only a few labeled stellate cells are in the upper molecular layer, mostly in superficial parts of lobules in the anterodorsal and central lobes. Consequently, by the morning of P10, neurogenesis in the basket cell population is complete and is nearing completion in the stellate cell population. It is now common to see unlabeled cells in the GRANULAR LAYER scattered amongst those that are heavily labeled, especially in the lingula, centralis, nodulus, and in deep parts of the other lobules. These are granule cells generated before the morning of P10. Labeled granule cells still predominate in superficial lobules of the anterodorsal and central lobes.
Most probable composition of the external germinal layer (egl):
1. Basket cell precursors are absent.
2. Only a few Stellate cell precursors are present.
3. All of the remaining and shrinking egl is populated with granule cell precursors.