Calcium and voltage dependence of single Ca2+-activated K+ channels from cultured hippocampal neurons of rat.
Calcium and voltage dependence of the Ca2+-activated K+ channel, K(Ca), was studied at the single-channel level in cultured hippocampal neurons from rat. The K(Ca) channel has approx. 220 pS conductance in symmetrical 150 mM K+, and is gated both by voltage and by Ca2+ ions. For a fixed Ca2+ concentration at the inner membrane surface, [Ca]i, channel open probability, Po, increases e-fold for 14 mV positive change in membrane potential. At a fixed membrane potential (0 mV), channel activity is first observed at [Ca]i = 10(-6) M, and increases with Ca2+ concentration approximating an absorption isotherm with power 1.4. The [Ca]i required to half activate (Po = 0.5) the channel is 4.10(-6) M. When compared to other preparations, the K(Ca) channel from hippocampal neurons reported here shows the lowest Ca2+ sensitivity and the highest voltage sensitivity. These findings are interpreted in evolutionary terms.
Franciolini
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F
Department of Physiology and Biophysics, University of Miami School of Medicine, FL.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006624:Hippocampus / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D009474:Neurons / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D051381:Rats
D007473:Ion Channels; D011188:Potassium; D002118:Calcium