Figure 1.

Percentage change in forearm blood flow (FBF) (left panel) and forearm vascular resistance (FVR) (right panel) during intra-arterial infusion of phentolamine (PHEN) for sildenafil (open circles) and placebo (filled squares). Percentage increase in FBF was significantly greater during infusion of PHEN after sildenafil administration compared with placebo administration (P = 0.001). Similarly, percentage reduction in FVR during PHEN was also significantly greater after sildenafil administration compared with placebo administration (P = 0.001). Abbreviation: ANOVA, analysis of variance.