Comparison of the effects of internal TEA+ and Cs+ on potassium current in squid giant axons.
Internal tetraethylammonium (TEA) and cesium ions block outward potassium current in nerve membrane in a voltage-dependent manner. Blockade with Cs+ occurs virtually instantaneously after membrane depolarization, whereas blockade with TEA+ occurs after a delay. The latter result suggested to Armstrong (1966, J. Gen. Physiol., 50:279-293; 1969, J. Gen. Physiol., 54:553-575) that potassium channels must open before TEA+ blockade can occur, which is in contrast to Cs+ blockade, which appears to be independent of channel gating. The results in this study concerning the effect of TEA+ on inward (tail) current argue against the Armstrong model. Specifically, TEA+ (partially) blocks inward current without altering the tail current time constant. This result indicates that TEA+ can occupy its binding site within the channel whether or not the channel gates are open. This alternative hypothesis can describe both the steady-state and time-dependent components of TEA+ blockade.
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Clay
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002586:Cesium / Q000494:pharmacology*; D049832:Decapodiformes; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D008959:Models, Neurological; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
D007473:Ion Channels; D013757:Tetraethylammonium Compounds; D002586:Cesium; D019789:Tetraethylammonium; D011188:Potassium