Fast, persistent, Ca2+-dependent K+ current controls graded electrical activity in crayfish muscle

Alfonso Araque, Washington Buño

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The early outward current in opener muscle fibres of crayfish (Procambarus clarkii) was studied using the two-electrode voltage-clamp technique. This current was abolished in Ca2+-free and 5 mM Cd2+ solutions, and was blocked by extra- or intracellular tetraethylammonium, indicating that it was a Ca2+-dependent K+ current [IK(Ca)]. IK(Ca) was voltage dependent, apamin insensitive and sensitive to charybdotoxin (CTX), which, in addition to its tetraethylammonium sensitivity, suggests that the channels mediating IK(Ca) behave in a BK type manner. IK(Ca) activation was extremely fast, reaching a maximum within 5 ms, and the inactivation was incomplete, stabilizing at a persistent steady-state. IK(Ca) was insensitive to intracellular ethylenebis(oxonitrilo)tetraacetate (EGTA), but was abolished by injection of the faster Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N∼'-tetraacetic acid (BAPTA), suggesting that voltage-dependent Ca2+ channels and those mediating IK(Ca) should be clustered closely on the membrane. Under two-electrode current-clamp recording mode, low amplitude, graded responses were evoked under control conditions, whereas repetitive all-or-none spikes were elicited by application of CTX or after loading the cells with BAPTA. We conclude that IK(Ca) activates extremely quickly, is persistent and is responsible for the generation and control of the low amplitude, graded, active responses of opener muscle fibres.

Original languageEnglish (US)
Pages (from-to)541-551
Number of pages11
JournalPflügers Archiv European Journal of Physiology
Volume430
Issue number4
DOIs
StatePublished - Aug 1 1995

Keywords

  • BAPTA
  • BK channels
  • Ca-dependent K current
  • Charybdotoxin
  • Crayfish muscle
  • EGTA
  • Graded electrical activity

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