Calcium-mediated decrease of a voltage-dependent potassium current.

D L Alkon; J J Shoukimas; E Heldman

doi:10.1016/s0006-3495(82)84479-2

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Calcium-mediated decrease of a voltage-dependent potassium current.

D L Alkon·J J Shoukimas·E Heldman

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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.

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D L Alkon, J J Shoukimas, E Heldman. 1982. Calcium-mediated decrease of a voltage-dependent potassium current.. https://doi.org/10.1016/s0006-3495(82)84479-2

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