Heart rate (HR) following ETA blockade by BQ610 in both normotensive and DOCA-salt hypertensive rats. HR was assessed as detailed in Materials and Methods and expressed as beats per minute ± SEM. (a) Basal HR. Basal values were registered 48 h before BQ610 administration; (b) Time course of HR. HR was registered following BQ610 administration at 24, 48, 72, 96, 120, and 144 h; (c) Average HR. Each bar represents the area under each curve (shown in b) between 0 and 144 h. Number of animals: control, 17; BQ610 (12 ng/h), 12; BQ610 (24 ng/h), 8; DOCA-salt, 17; DOCA-salt + BQ610 (12 ng/h), 11; and DOCA-salt + BQ610 (24 ng/h), 10.