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

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 cortex2,3, and also in connection with the development and maintenance of normal dendritic structures of P cells4–7. 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 nuclei8,9. This not only urges reinterpretation of the symptoms arising from destruction of the IO10,11, 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.