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Updated: Aug 10, 2026

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
Published on: January 11, 2011
Rundown of the hyperpolarization-activated KAT1 channel involves slowing of the opening transitions regulated by
1Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242, USA.
Abstract:
Disappearance of the functional activity or rundown of ion channels upon patch excision in many cells involves a decrease in the number of channels available to open. A variety of cellular and biophysical mechanisms have been shown to be involved in the rundown of different ion channels. We examined the rundown process of the plant hyperpolarization-activated KAT1 K+ channel expressed in Xenopus oocytes. The decrease in the KAT1 channel activity on patch excision was accompanied by progressive slowing of the activation time course, and it was caused by a shift in the voltage dependence of the channel without any change in the single-channel amplitude. The single-channel analysis showed that patch excision alters only the transitions leading up to the burst states of the channel. Patch cramming or concurrent application of protein kinase A (PKA) and ATP restored the channel activity. In contrast, nonspecific alkaline phosphatase (ALP) accelerated the rundown time course. Low internal pH, which inhibits ALP activity, slowed the KAT1 rundown time course. The results show that the opening transitions of the KAT1 channel are enhanced not only by hyperpolarization but also by PKA-mediated phosphorylation.
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