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  • Title: Survival of K+ permeability and gating currents in squid axons perfused with K+-free media.
    Author: Almers W, Armstrong CM.
    Journal: J Gen Physiol; 1980 Jan; 75(1):61-78. PubMed ID: 7359118.
    Abstract:
    K+ currents were recorded in squid axons internally perfused with impermeant electrolyte. Total absence of permeant ions inside and out leads to an irreversible loss of potassium conductance with a time constant of approximately 11 min at 8 degrees C. Potassium channels can be protected against this effect by external K+, Cs+, NH4+, and Rb+ at concentrations of 100-440 mM. These experiments suggest that a K+ channel is normally occupied by one or more small cations, and becomes nonfunctional when these cations are removed. A large charge movement said to be related to K+ channel gating in frog skeletal muscle is absent in squid giant axons. However, deliberate destruction of K+ conductance by removal of permeant cations is accompanied by measurable loss in asymmetric charge movement. This missing charge component is large enough to contain a contribution from K+ gating charge movements of more than five elementary charges per channel.
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