TRESK background potassium channel is not gated at the helix bundle crossing near the cytoplasmic end of the pore
A, TREK-1 channels were expressed in HEK293T cells and recordings were done on excised inside-out patches. TREK-1 currents were measured at +60 mV by switching the K+-free bath solution to a high K+ solution (solution changes are marked with bars above the graphs). In this representative recording, TREK-1 channels were activated by perfusing the intracellular side of the patch with acidic solution (pH 6.1) as shown on the graph. Barium (1 mM) was applied at a holding potential of -80 mV and block was initiated by depolarizing the membrane to +60 mV (application of Ba2+ is marked by a bar above the recording and changes in the membrane potential are shown under the recording). B, The pH of the bath solution was 7.1 throughout the experiment. In this representative recording, Ba2+ (1 mM) was applied at a holding potential of -80 mV and block was initiated by depolarizing the membrane to +60 mV (see the vertical arrow, application of Ba2+ is marked by a bar above the recording and changes in the membrane potential are shown under the recording.). C, The kinetics of Ba2+ induced TREK-1 block were determined for both the resting (perfused with pH 7.1 solution) and activated (pH 6.1) channel (n = 8 and 6 patches). The averaged normalized curves are plotted for both groups. The inset shows the onset of Ba2+ block at an early time period with higher temporal resolution. D, The current recordings of the Ba2+ block recorded at different pH values were fitted with a double exponential equation. The time constants of the fitted equations are plotted as a scatter plot. The average values are plotted as columns. Differences between the groups were not statistically significant.