Novel description of the large conductance Ca2+ -modulated K+ channel current, BK, during an action potential from suprachiasmatic nucleus neurons
Abstract
The contribution of the large conductance, Ca2+-modulated, voltage-gated K+ channel current, IBK, to the total current during an action potential (AP) from suprachiasmatic nucleus (SCN) neurons is described using a novel computational approach. An experimental recording of an SCN AP and the corresponding AP-clamp recording of IBK from the literature were both digitized. The AP data set was applied computationally to a kinetic model of IBK that was based on results from a clone of the BK channel α subunit heterologolously expressed in Xenopus oocytes. The IBK model result during an AP was compared with the AP-clamp recording of IBK The comparison suggests that a change in the intracellular Ca2+ concentration does not have an immediate effect on BK channel kinetics. Rather, a delay of a few milliseconds may occur prior to the full effect of a change in Cai2+ As shown elsewhere, the β2 subunit of the BK channel in the SCN, which is present in the daytime along with the α subunit, shifts the BK channel activation curve leftward on the voltage axis relative to the activation curve of BK channels comprised of the α subunit alone. That shift may underlie the diurnal changes in electrical activity that occur in the SCN and it may also ...Continue Reading
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