Climbing Fibre Plasticity in the Cerebellum of the Adult Rat

The present paper reports an example of collateral sprouting, and provides a detailed morphological description of newly formed axonal branches, terminal arborizations, and synapses in the central nervous system of an adult mammal. By means of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L), we demonstrate that the climbing fibres, which survive a subtotal lesion of the inferior olive in the rat, emit collateral sprouts and develop new terminal plexuses forming new synaptic contacts on Purkinje cell dendrites. Adult climbing fibres thus show striking plastic capabilities that represent the morphological basis of the functional reinnervation of Purkinje cells.