Ion conductance of the Ca(2+)-activated maxi-K+ channel from the embryonic rat brain.
By using single-channel recording techniques, we measured the conductance (gK) of the Ca(2+)-activated Maxi-K+ channel from the embryonic rat brain, and examined its dependence on K+ ions present in equimolar concentrations on both sides of the membrane patch. With ionic strength maintained constant by substitution of N-methyl-D-glucamine for K+, gK has a sigmoidal dependence upon [K+]. This result has been obscured in previous work by variations in ionic strength, which has a marked effect on single-channel conductance, especially in the limit for which this variable approaches zero. The gK versus [K+] relationship is described, theoretically, by a three-barrier, two-binding-site model in which the barrier that an ion must cross to leave the channel is decreased as [K+] is increased.
Mienville
J M
JM
Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA. jmm@psych.uic.edu
Clay
J R
JR
D000818:Animals; D001921:Brain / Q000502:physiology*; D004553:Electric Conductivity; D004622:Embryo, Mammalian; D007700:Kinetics; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008536:Meglumine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D051381:Rats
D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D008536:Meglumine; D011188:Potassium