Abstract
The pharmacological and single-channel properties of Ca 2+ channels were studied in the somata and dendrites of adult cerebellar Purkinje cells. The Ca 2+ channels were exclusively of the high threshold type: low threshold Ca 2+ channels were not found. These high threshold channels were not blocked by cu-conotoxin GVIA and were inhibited rather than activated by BAY K 8644. They were therefore pharmacologically distinct from high threshold N- and L-type channels. Funnel web spider toxin was an effective blocker. The channels opened to conductance levels of 9, 14, and 19 pS (in 110 mM Ba 2+). These slope conductances were in the range of those reported for N- and L-type channels. Our results are in agreement with previous reports suggesting that Ca 2+ channels in Purkinje cells can be classified as P-type channels according to their pharmacology. The results also suggest that distinctions among Ca 2+ channel types based on the single-channel conductance are not definitive.
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