Potassium channels activated by sodium.
Na+-activated K+ currents have been reported in snail neurones, crayfish giant motoneurones, cardiac myocytes, and in ganglion cells and brain stem cells from chick embryos. Such currents are seen in voltage-clamp experiments, following depolarization-induced Na+ influx. A variety of experiments have shown that the currents through the conductance pathways are indeed carried by K+ ions and that they are quantitatively dependent upon Na+ influx into the cells. Theoretical calculations indicate that such currents must make a substantial contribution to action potential repolarization. The conductances are activated by Li+ in invertebrate neurones, but not in the embryonic vertebrate neurones. Single-channel recordings from vertebrate brain stem cells reveal channels with conductances of about 50 pS, activated by Na+ concentrations in the 10-100 mM range.
Martin
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Department of Physiology, University of Colorado School of Medicine, Denver 80262.
Dryer
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D000818:Animals; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects*; D012964:Sodium / Q000494:pharmacology*
D015221:Potassium Channels; D012964:Sodium