[Cerebellar disfacilitation after pharmacological destruction of the inferior olive]

The total selective destruction of the inferior olive by 3-acetylpyridine produces a marked increase in the metabolic activity at the intracerebellar nuclei. This increase is locally suppressed by partial ablation or local inactivation of the corresponding regions in the cerebellar cortex, suggesting its localization in the intranuclear presynaptic terminals of the Purkinje cells. In a second series of experiments, it is demonstrated that Purkinje cells of the cerebellar cortex deprived of their climbing fibers and therefore of their complex spikes by destruction of the inferior olive, increase their firing frequency of simple spikes. As a consequence, there is a decreased frequency of discharge of their target neurones in the intracerebellar nuclei; the net result of suppression of the inferior olive is thus an increased cortico-nuclear inhibitory effect.