Dendritic plateau potentials evoked in Purkinje cells by parallel fibre volleys in the cat.

Responses evoked in Purkinje cell dendrites by parallel fibre volleys and climbing fibre impulses were investigated by intra- and extracellular recording from cat cerebellar cortex. The depth distribution of recording sites suggested that the intracellular recordings were predominantly from proximal dendrites whereas the extracellular recordings were predominantly from distal dendrites. Parallel fibre stimulation evoked monosynaptic excitation and disynaptic inhibition in the dendrites and, at higher strength, prolonged plateau-like responses in distal dendrites but only rarely in proximal dendrites. However, when the inhibitory synapses were blocked with topically applied picrotoxin, parallel fibre volleys evoked plateau potentials also in proximal dendrites. The duration of the parallel-fibre-evoked plateau potentials in distal dendrites was prolonged by increasing the intensity of the eliciting stimulus or by increasing the number of stimuli. A similar prolongation in the duration of climbing-fibre-evoked plateau potentials was observed when brief repetitive stimulation was applied to the inferior olive. The investigation provided evidence that under physiological conditions plateau potentials in Purkinje cell dendrites are exclusively evoked by climbing fibre impulses.