Chick cerebellar purkinje cells express ω-conotoxin GVIA-sensitive rather than funnel-web spider toxin-sensitive calcium channels

Abstract

Voltage-gated calcium channels form a complex family of distinct molecular entities which participate in multiple neuronal functions. In cerebellar Purkinje cells these channels contribute to the characteristic electrophysiological pattern of complex spikes, first described in birds 7 and later in mammals. 9 A specific calcium channel, the P-type channel, 10 has been shown to mediate the majority of the voltage-gated calcium flux in mammalian Purkinje cells. 13, 25 P-type channels play an essential role in synaptic transmission of mammalian cerebellum. 15, 16, 20, 22 It is unclear whether the P-type calcium channel is present in birds. Studies in chick synaptosomal preparations show that the pharmacological profile of calcium channels is complex 1, 12 and suggest a minimal expression of the P-type channel in avian central nervous system. In the present work, we studied voltage-gated calcium channels in dissociated chick cerebellar Purkinje cells to examine the presence of different calcium channel types. Purkinje cells were used because, in mammals, they express predominantly P-type channels and because the morphology of these cells is thought to be phylogenetically conserved. 21 We found that ω-conotoxin GVIA ω-CgTx GVIA):, a specific antagonist of N-type calcium channel, rather than the synthetic funnel-web spider toxin (sFTX), a P-type channel antagonist, blocks the majority of the barium current flowing through calcium channels in chick Purkinje neurons.