Concentration-response curves for pulmonary artery constriction by KCNQ channel blockers. Concentration dependence of contraction induced by linopirdine (A) or XE991 (B) in rat intrapulmonary arteries that were intact (+E) or denuded of endothelium (-E). Plots also show the mean responses of rat mesenteric arteries (MA) at the same drug concentrations. Each point represents the mean ± SEM of 5–6 experiments. C. Concentration dependence of contraction induced by linopirdine (n = 9) or XE991 (n = 11) in intact mouse intrapulmonary arteries. Responses were measured in each vessel as a percentage of the contractile response to 50 mM KCl.