Figure 6.

Effect of KCNQ activators on SMC currents and resting membrane potential. (A) Example of a family of outward currents in SMC enhanced by flupirtine (20 μM). (B) Summary of six similar experiments in which flupirtine significantly reduced the outward current at potentials between −50 and +10 mV. (C) The current evoked by stepping to 0 mV had both inward and outward components. Flupirtine reduced the inward component at the beginning of the trace and increased the outward current over the remainder of the sweep. Right panel shows an inward Ca²⁺ current (at 0 mV), which was recorded using Cs⁺-filled electrodes in order to eliminate outward K⁺ currents. Flupirtine reduced the inward current amplitude. (D) Example of a current-clamp recording where flupirtine (20 μM) caused a reversible membrane hyperpolarization in quiescent cells (left panel). Cells which exhibited spontaneous electrical activity in the absence of drugs (right panel) ceased firing on hyperpolarization induced by flupirtine. (E) Meclofenamic acid (MFA, 20 μM) increased amplitude of currents at +40 mV. (F) Summary bar chart showing significant enhancement of current amplitude by MFA in 11 cells. *P < 0.05, significantly different from control.