Properties of the slow K+ current of the nodal membrane.
1. In voltage clamped myelinated nerve fibres, some properties of the slow K+ current (Dubois, 1981 b) were analysed under different experimental conditions. 2. The instantaneous slow current-voltage relationships are linear in low and high K+ solutions, and the variation of the reversal potential with external K+ concentration agrees with the predicted Nernst changes for the K+ equilibrium potential. 3. Li+, Na+ and Cs+ are virtually impermeant in the slow channels. Rb+ is permeant and the permeability ratio PRb/PK (calculated from the reversal potential and the Goldman-Hodgkin-Katz equation) is a function of the external K+ and Rb+ concentrations. 4. External and internal Cs+ block respectively the slow inward and outward K+ current and the block is voltage dependent. 5. The closing kinetics of the slow channels are independent of the external K+ concentration but depend on the conditioning pulse duration.
D000818:Animals; D002414:Cations, Monovalent; D002586:Cesium / Q000494:pharmacology; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D011901:Ranvier's Nodes / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D002414:Cations, Monovalent; D007473:Ion Channels; D002586:Cesium; D013779:Tetrodotoxin; D011188:Potassium