Effect of acute atenolol on short-term blood pressure variability and baroreflex sensitivity in rats

Beta-blocker therapy for hypertension or coronary artery disease is common, but there are a lot of controversies about its effects on short-term blood pressure variability and arterial baroreceptor reflexes. The aim of this s tudy was to evaluate the effects of acute atenolol on baroreflex sensitivit y (BRS) and on the spontaneous variability of systolic blood pressure (SBP) and RR intervals in conscious rats. Ten Wistar rats equipped with telemetr y system were evaluated: 1) under control conditions; 2) after injection of saline; and 3) during beta(1)-adrenergic blockade by atenolol. Fast Fourie r transform analysis was applied to RR intervals and SEP. Atenolol increase d RR intervals significantly by 14% and the variation coefficient of the RR intervals by 31%. SEP was reduced significantly by 9%. In frequency domain , beta(1)-blockade in RR intervals increased very low frequency by 33%, and the total power by 22% and decreased low frequency by 25%. The ratio of lo w to high frequency power decreased by 60%. Frequency domain variables in S EP were not significantly changed after beta(1)-adrenergic receptor blockad e. BRS (gain alpha) was not significantly altered by beta-blockers. Acute a tenolol decreased SEP and increased RR intervals with no change in BRS, ind icating 'resetting' of baroreflex function. (C) 2000 Editions scientifiques el medicales Elsevier SAS.