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PubMed · 6090580

Calcium mediates the light-induced decrease in maintained K+ current in Limulus ventral photoreceptors.

K Chinn·J Lisman
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Abstract

In addition to increasing the conductance to sodium, light reduces the maintained voltage-dependent potassium current (iK) in Limulus ventral photoreceptors. We have investigated the mechanism underlying this long-lasting decrease in ik. Intracellular injection of calcium produced a similar reduction of the voltage-dependent outward current. This reduction was not due to an activation of the voltage-dependent inward current (iin) because calcium injection reduced the outward current even under conditions where iin was blocked with Ni2+, and because calcium injection produced a decrease in conductance, as measured from the slope of the instantaneous i-V curve. The effect of light on ik could be blocked by injection of the calcium buffer EGTA (pCa 7.1) to an intracellular concentration of 50-70 mM. Even larger injections of the pH buffer MOPS (100-200 mM) did not reduce the effect of light on ik. These experiments show that intracellular free calcium (Cai2+) can reduce ik. Furthermore, since Cai2+ is known to increase in light, our results are consistent with the hypothesis that calcium is the internal transmitter for the light-induced decrease in ik.

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AnimalsBuffersCalciumEgtazic AcidHorseshoe CrabsInjections, JetIon ChannelsLightMorpholinesPhotoreceptor CellsPotassiumJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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K Chinn, J Lisman. 1984. Calcium mediates the light-induced decrease in maintained K+ current in Limulus ventral photoreceptors.. https://doi.org/10.1085/jgp.84.3.447

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