Fig. 2. Effects of lung perfusion with 0.01, 0.1, and 1.0 mm 4-aminopyridine (4-AP) on intrinsic vascular resistance (R⁰;  A ), representing pulmonary vascular resistance that would exist if the vessels were at their respective diameter at zero vascular pressure, and on vessel distensibility (α;  B ) according to nonlinear regression analysis of the pulmonary vascular pressure–flow relation in lungs obtained from lipopolysaccharide-treated (•) and untreated control (○) mice (n = 7 per group). hx = hypoxic ventilation; nx = normoxic ventilation; w/o 4-AP = no 4-aminopyridine was added to the perfusate. *  P < 0.05  versus w/o 4-AP. †  P < 0.05  versus control. Data are presented as mean ± SD.