Existence of very weak level of residual multiple innervation of Purkinje cells through climbing fibers in the cerebellum of the normal adult rat

Extra- or intracellular unit responses of Purkinje cells to the activation of climbing fibres were recorded in the cerebellum of adult rats. Out of 1.719 cels studied, only 4 were found to be innervated by more than one climbing fibre. This very small rate of residual multiple innervation in the normal adult illustrates the accuracy of the synaptic elimination process which leads to the innervation of each Purkinje cell through only one climbing fibre during normal development in the rat.