Fig. 3. Effect of sildenafil (50 mg via  nasogastric tube) and zaprinast (2 mg/kg over 5 min loading dose followed by infusion of 0.1 mg · kg⁻¹· min⁻¹intravenously) on the magnitude (A ) and the duration (B ) of the change in PAP induced by inhalation of 2.5, 10, and 40 ppm NO. Clear bars = control values before administration of sildenafil or zaprinast. Black bars = values after administration of sildenafil or zaprinast. *P < 0.001 versus  control; †P < 0.001 versus  the sildenafil group. n = 7 in the sildenafil group; n = 5 in the zaprinast group. Data are expressed as mean ± SE.