Regression analysis of total amount of water ingested in 3 h postinjection of vehicle or minoxidil plotted against average change in mean arterial pressure (ΔMAP) postinjection for young, middle-aged, and old rats. Intakes are adjusted for body weight. All correlations were statistically significant. The slopes of the regression lines were significantly different (P <0.01). Regression equations: young, y = 0.11–0.055x; middle-aged, y = 0.14–0.031x; old, y = 0.12–0.01x.