Tetrodotoxin-resistant dendritic spikes in avian Purkinje cells.

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Abstract
Electrophysiological evidence for the existence of dendritic spikes in the Purkinje cells of pigeon cerebellar cortex was presented. Intradendritic records indicated that the electroresponsive properties of the dendrites linger after voltage-dependent Na+ and K+ conductances were reduced by superfusion of the cortex with Ringer''s solution containing 20 .mu.g/ml tetrodotoxin and 5 mM 3-aminopyridine. Dendritic spikes could be evoked, in the complete absence of activity from all cerebellar afferents and from the soma and axon of the Purkinje cells, by direct electrical activation of the surface of the cerebellar cortex or by intracellular injection of current via the recording electrode. The dendritic electroresponsiveness was blocked by superfusion with 20 mM Mn2+ or Co2+. Dendrites of Purkinje cells in birds are apparently capable of generating Ca2+-dependent spikes. The possible role of such a Ca2+ current in neuronal function is discussed.