Fig. 8.
Suppression of Kv7 currents by bronchoconstrictor agonists in guinea pig ASMCs and their restoration by the Kv7 channel activator flupirtine. A: the time course of Kv7 current inhibition was recorded in ASMCs, at −20 mV holding voltage in control (2 min) following by methacholine application (100 nM for 3 min). Time course was disrupted for 10 min for recording of steady-state I-V curves (time break indicated by vertical gray lines). After an additional 1-min recording, flupirtine (10 μM) was applied in the presence of methacholine (C = 21 pF, representative of 4 similar experiments). B: average I-V relationships of Kv7 currents recorded from −4 mV holding voltage in ASMCs before (control, ●, n = 4), during treatment with 100 nM methacholine (○, n = 4), and in the presence of XE991 (10 μM, ▲, n = 3) applied in the end of each experiment to confirm that recorded current are indeed Kv7 currents. C: dose-dependent suppression of Kv7 currents recorded at −20 mV holding voltage was observed upon application of histamine (3–30 μM, indicated by arrows). D: average I-V relationships of Kv7 currents recorded from −4 mV holding voltage and normalized to control currents recorded at +1 mV in control (●, n = 4), in the presence of 30 μM histamine (○, n = 4) and in the presence of XE991 (10 μM, ▲, n = 4). E: normalized currents recorded at −20 mV in control (solid bars), in the presence of agonists (open bars: His, 30 μM histamine, n = 4; MC, 100 nM methacholine, n = 4); in the presence of agonists plus 10 μM flupirtine (hatched bars: His+F, 10 μM flupirtine in the presence of 30 μM histamine, n = 4; MC+F, 10 μM flupirtine in the presence of 100 nM methacholine, n = 4) and in the presence of 10 μM XE991 (n = 4). Ic, control current measured before treatment. *Significant difference from control (P < 0.05, 1-way ANOVA). #Significant difference from all other treatment (P < 0.05, 1-way ANOVA).