Single apamin-blocked Ca-activated K+ channels of small conductance in cultured rat skeletal muscle

Andrew L. Blatz, Karl L. Magleby

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Abstract

Action potentials in many excitable cells are followed by a prolonged afterhyperpolarization that modulates repetitive firing. Although it is established that the afterhyperpolarization is produced by Ca-activated K+ currents, the basis of these currents is not known. The large conductance (250 pS) Ca-activated K+ channel (BK channel) is not a major contributor to the afterhyperpolarization in non-innervated skeletal muscle and some nerve cells, because apamin, a neurotoxic component of bee venom, abolishes the afterhyperpolarization but does not block BK channels, and 5 mM extracellular tetraethylammonium ion (TEA) blocks BK channels but does not reduce the afterhyperpolarization. We now report single-channel currents from small conductance (10-14 pS) Ca-activated K+ channels (SK channels) with the necessary properties to account for the afterhyperpolarization. SK channels are blocked by apamin but not by 5 mM external TEA (TEA(o)). They are also highly Ca-sensitive at the negative membrane potentials associated with the afterhyperpolarization.

Original languageEnglish (US)
Pages (from-to)718-720
Number of pages3
JournalNature
Volume323
Issue number6090
DOIs
StatePublished - Dec 1 1986

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