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. 2009 Mar 16;587(Pt 10):2225–2231. doi: 10.1113/jphysiol.2008.163550

Figure 1. KCNQ4 channels, but not BK channels, are sensitive to osmotically induced challenges.

Figure 1

A, original QPatch I–t traces showing the effects of changes in extracellular osmolarity on BK and KCNQ4 currents recorded from QPatch experiments on HEK 293 cells (whole-cell configuration). KCNQ4 and BK channels were activated by a step-protocol under iso-, hypo- and hyperosmotic conditions. For BK, from a holding potential of −80 mV, steps of 10 mV (200 ms duration) were applied from −80 mV to 110 mV. For KCNQ4, from a holding potential of −80 mV, steps of 20 mV (2 s duration) were applied from −100 mV to 80 mV. Zero current is indicated by the horizontal line. Ion composition on the cis and trans sides is given in mm (rightmost panels). B, effects of changes in extracellular osmolarity for all experiments on KCNQ4 (n= 12) and BK (n= 10) current–voltage relationship recorded in QPatch experiments on HEK 293 cells. Currents were normalized relative to maximal steady-state currents under isosmotic conditions. The data are means (±s.d.) currents.