Effect of the KCNQ potassium channel opener retigabine on single KCNQ2/3 channels expressed in CHO cells

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Abstract
KCNQ2/3 potassium channel subunits were co‐expressed in Chinese hamster ovary (CHO) cells and currents through single channels recorded using cell‐attached patches. Channels had a similar slope conductance in the presence (8.04 ± 0.02 pS) and absence (7.6 ± 0.01 pS) of 10 μm retigabine. The mean maximal open probability (Po) for single KCNQ2/3 channels was 0.13 ± 0.02, with a half‐maximal Po potential (Vo) of −28.7 ± 1.4 mV for control recordings. Retigabine increased mean maximal Po to 0.38 ± 0.04 and produced a hyperpolarising shift of Vo to −40.1 ± 3.4 mV. Single KCNQ2/3 channels have multiple voltage‐dependent kinetic components in their activity (CL‐OS‐CM‐OL‐CS; C = closed, O = open, L = long, S = short, M = medium), giving short, medium and long closed times (τCS, τCM, τCL) and short and long open times (τOS and τOL). In the presence of retigabine at 0 mV the combined duration and contributions of the longest closed time τCL decreased tenfold, while the short and long open times increased fourfold and twofold, respectively. Thus, steady‐state kinetics were modified to favour the open channel configuration.