Calcium-mediated decrease of a voltage-dependent potassium current

D. L. Alkon, J. J. Shoukimas, E. Heldman

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    39 Scopus citations

    Abstract

    Elevated intracellular Ca++ concentration reduces the amplitude of an early, voltage-dependent K+ current (IA) in the Type B photoreceptor of Hermissenda crassicornis. Internal Ca++ is increased by activating a voltage and light-dependent Ca++ current present in these cells or by direct iontophoresis of Ca++ ions. Substitution of Ba++ for Ca++ or elimination of Ca++ from the sea water bathing the cells abolishes the reduction in IA during paired light and depolarizing voltage steps. The delayed K+ current (IB) in these cells is also reduced during paired light and voltage steps, but this decrease of IB is not affected by removal of extracellular Ca++. IB (but not IA), apparently much less dependent on intracellular Ca++ levels, is reduced by light alone. Ca++ iontophoresis also abolishes the light-dependent Na+ current, which recovers with a time course of minutes.

    Original languageEnglish
    Pages (from-to)245-250
    Number of pages6
    JournalBiophysical Journal
    Volume40
    Issue number3
    DOIs
    StatePublished - 1 Jan 1982

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