Stability of multiple innervation of Purkinje cells by climbing fibers in the agranular cerebellum of old rats X-irradiated at birth.

In the cerebellum of old X-irradiated rats, the multiple innervation of Purkinje cells by climbing fibers, which normally regresses after birth, was still present up to 18 months. Furthermore, the mean number of synaptic contacts upon each Purkinje cell was not smaller than what is observed in young adults, indicating that, after irradiation, these redundant synapses are definitively stabilized.