Destruction of inferior olive induces rapid depression in synaptic action of cerebellar Purkinje cells

Abstract

THE climbing fibre afferents (CFAs) are a structure unique to the cerebellar cortex; they originate, presumably solely, from the inferior olive (IO) and make an extensive, excitatory synaptic contact with dendrites of cerebellar Purkinje cells (P cells)¹. The importance of the CFAs in cerebellar functions has been emphasised in connection with the learning process which may occur in the cerebellar cortex^2,3, and also in connection with the development and maintenance of normal dendritic structures of P cells^4–7. An interesting recent finding is that after destruction of the IO electrical stimulation of the cerebellar cortex fails to elicit the normal inhibitory synaptic action of P cells on their target neurones in vestibular nuclei^8,9. This not only urges reinterpretation of the symptoms arising from destruction of the IO^10,11, but also raises a basic general problem of remote interaction in neuronal networks. Here, we report that the depression of the P-cell action develops unexpectedly fast following destruction of the IO, and also present evidence indicating that this remote effect is mediated largely by a non-impulse transmission process, presumably an axonal flow, in CFAs and P-cell axons.