PMID: 2121887Sep 1, 1990Paper

Properties of potassium currents and their role in membrane excitability in Drosophila larval muscle fibers

The Journal of Experimental Biology
S Singh, C F Wu

Abstract

The larval muscle fibers of Drosophila show four outward K+ currents in addition to the inward Ca2+ current in voltage-clamp recordings. The Shaker (Sh) and the slowpoke (slo) mutations, respectively, eliminate the voltage-activated fast K+ current (IA) and the Ca2(+)-activated fast K+ current (ICF). Quinidine specifically blocks the voltage-activated delayed K+ current (IK) at micromolar concentrations. We used Sh, slo and quinidine to remove specifically one or more K+ currents, so as to study physiological properties of these currents not previously characterized, and to examine their role in membrane excitability. A linear relationship was observed between the peak ICF and the peak ICa at different membrane potentials. ICF inactivated considerably during a 140 ms pulse to +20 mV. Recovery from inactivation was not complete for up to 2 s at the holding potential of -50 mV, which is much slower than the recovery of Ca2+ current from inactivation. In addition to IA and ICF, two delayed K+ currents are also observed in these fibers, the voltage-activated IK and the Ca2(+)-activated ICS. Near the end of a 500 ms depolarizing pulse, both IA and ICF are inactivated. Ca2(+)-free and 20 mmol l-1 Ca2+ saline were used to examine the ...Continue Reading

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