Functional aspects of the inferior olive.
A review is presented of a series of recent experiments aimed at studying the effects of irreversible lesion and of reversible inactivation of the inferior olive. Following a permanent lesion of the inferior olive, no alteration has been found: i) in the morphology of the synapse between Purkinje and Deiters neurones, and ii) in the inhibitory properties of the three types of cells of the cerebellar cortex innervated by the olivocerebellar pathway: the Purkinje, the Golgi and the basket cells. Following reversible inactivation of the inferior olive of one side by cooling, a remarkable increase of the simple spike activity has been found in all the Purkinje cells showing a disappearance of the climbing fibre activity. This effect is likely mediated, at a large extent, by climbing fibre collaterals through corticocerebellar interneurones. The same reversible inactivation of the inferior olive induces a drastic reduction of the activity in the cells of intracerebellar and vestibular nuclei. These experiments don't provide support for a trophic function of the inferior olive on its target neurones. They suggest that this nucleus exerts a very powerful tonic inhibitory action on Purkinje cells and consequently a control on the excitability of intracerebellar and subcerebellar centres. Such a control is likely important for the processing of informations through the cerebellum and therefore for the control of motor activities.
D000200:Action Potentials; D000818:Animals; D003080:Cold Temperature; D004594:Electrophysiology; D009433:Neural Inhibition; D009847:Olivary Nucleus / Q000502:physiology*; D011689:Purkinje Cells / Q000502:physiology; D051381:Rats; D013569:Synapses / Q000502:physiology