Delayed activation of large-conductance Ca2+-activated K channels in hippocampal neurons of the rat

Biophysical Journal
Y IkemotoN Akaike

Abstract

We applied a fast concentration jump system to produce step changes in Ca2+ concentration [( Ca2+]i) on the cytoplasmic side of the inside-out membrane patch, excised from isolated rat hippocampal pyramidal neurons, and examined the time course of the activation phase of the large-conductance K channel (the BK channel; approximately 266 pS) after a step rise in [Ca2+]i. Diffusion of Ca2+ from the electrode tip to the cytoplasmic surface of the patch was estimated to be almost completed in 10 ms. After a step increase in [Ca2+]i from 0.04 to 3.2-1,000 microM, the activation of the K channel started after a clear latency of 280-18 ms and proceeded along a sigmoidal function. This was in sharp contrast with the rapid deactivation that began without delay and that was completed within 50 ms. The latency in activation was not accounted for by the binding of Ca2+ to EGTA in unstirred layers in the patch, since this binding was reported to be slow, taking up to seconds at physiological pH. Calmodulin (1 microM) did not affect the delay, the activation rate, or the steady-state current level. The calmodulin inhibitors W-7 and W-5 caused flickering of the single-channel current. These results indicate a delayed activation of the BK chan...Continue Reading

Citations

Sep 6, 2015·Journal of the Neurological Sciences·Weiwei YuChenhong Li
Mar 30, 2004·The Journal of Physiology·Xiao-Ping SunAlan D Grinnell
Feb 12, 2019·Annual Review of Physiology·Vivian Gonzalez-Perez, Christopher J Lingle

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