Neuron
Volume 11, Issue 2, August 1993, Pages 291-303
Journal home page for Neuron

Article
Distinctive biophysical and pharmacological properties of class A (BI) calcium channel α1 subunits

https://doi.org/10.1016/0896-6273(93)90185-TGet rights and content

Abstract

Transcripts for the class A Ca2+ channel α1 subunit (also known as BI) are present at high levels in many parts of the mammalian CNS and are widely assumed to encode the P-type Ca2+ channel. To characterize the biophysical and pharmacological properties of α1A channels, macroscopic and single-channel recordings were made in Xenopus oocytes injected with α1A cRNA. α1-specific properties were identified by making systematic comparisons with the more familiar class C α1 subunit under the condition of a standard ancillary subunit (α2/δ + β) makeup. α1A currents activate and inactivate more rapidly and display steeper voltage dependence of gating than α1C currents. Unlike α1C, α1A channels are largely insensitive to dihydropyridines and FPL 64176, but respond to the cone snail peptide ω-CTx-MVIIC (SNX-230), a potent and fairly selective inhibitor. In comparison with P-type Ca2+ channels in rat cerebellar Purkinje cells, α1A channels in oocytes are ∼102-fold less sensitive to ω-Aga-IVA and ∼10-fold more sensitive to ω-CTx-MVIIC. α1A channels are not inhibited by Bay K 8644 and inactivate much more rapidly than P-type Ca2+ channels. Thus, α1A is capable of generating a Ca2+ channel phenotype quite different from P-type current.

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