Cs(+) causes a voltage-dependent block of inward K currents in resting skeletal muscle fibres.
When frog skeletal muscle fibres are bathed in solutions containing Cs(+) and K(+) in the ratio 1:4,000, a reduction is observed in the size of inward K currents through the resting membrane. This effect is enhanced by an increase in either hyperpolarisation or external Cs(+) concentration. It can be predicted from these findings that regenerative changes in membrane potential should be obtainable in fibres, in the presence of Cs(+), that are hyperpolarised by means of a current electrode. Such responses are described in the last part of this report. In squid axon and frog node, internal Cs(+) produces a voltage-dependent block of the delayed, outward K currents, though the ratio of Cs(+) to K(+) required for this effect is far greater than that used in the experiments reported here. A closer parallel can be drawn between our findings and those recently reported on the inward K currents in the starfish egg cell.
Gay
L A
LA
Department of Physiology, University of Leicester, UK.
Stanfield
P R
PR
D000818:Animals; D002586:Cesium / Q000378:metabolism / Q000494:pharmacology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011896:Rana temporaria
D002586:Cesium; C025407:cesium sulfate; D011188:Potassium