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1 Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
2 Department of Physiology, Oxford University, Oxford, Oxon, United Kingdom
* To whom correspondence should be addressed. E-mail: keith.buckler{at}physiol.ox.ac.uk.
The single channel properties of TASK-like oxygen-sensitive potassium channels were studied in rat carotid body type-1 cells. We observed channels with rapid bursting kinetics, active at resting membrane potentials. These channels were highly potassium selective with a slope conductance of 14-16 pS, values similar to those reported for TASK-1. In the absence of extracellular divalent cations, however, single channel conductance increased to 28 pS in a manner similar to that reported for TASK-3. Following patch excision, channel activity ran down rapidly. Channel activity in inside-out patches was markedly increased by 2 mM and 5 mM ATP and by 2 mM ADP but not by 100µM ADP or 1 mM AMP. In cell attached patches both cyanide and 2,4-dinitrophenol strongly inhibited channel activity. We conclude that 1) whilst the properties of this channel are consistent with it being a TASK-like potassium channel they do not precisely conform to those of either TASK-1 or TASK-3, 2) channel activity is highly dependent upon cytosolic factors including ATP, and 3) that changes in energy metabolism may play a role in regulating the activity of these background-K+-channels.
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