Acute effects of third generation β-blockers on short-term and beat-to-beat blood pressure variability in sinoaortic-denervated rats

Abstract

An increase in blood pressure variability (BPV) contributes to the development of target organ damage associated with hypertension. Treatment with conventional b-blockers, such as atenolol, has been associated with an increase in BPV; however, the extrapolation of these results to third generation b-blockers with pleiotropic effects seems to be inappropriate. The cardiovascular effects of third generation b-blockers, carvedilol and nebivolol, were assessed in sinoaortic-denervated rats (SAD) and compared with the second generation b-blocker atenolol and the calcium channel blocker verapamil, with a special focus on short-term BPV. Male SAD rats were acutely treated with carvedilol, nebivolol, atenolol or verapamil at two different doses, and the effects on blood pressure and BPV were recorded. Short-term BPV was assessed by the s.d. of BP recordings. Beat-tobeat BPV was studied using spectral analysis to assess the vascular sympatholytic activity of carvedilol and nebivolol by estimating the effects of these drugs on the ratio of low frequency (LF) to high frequency (HF) BPV (LF/HF ratio). Nebivolol, carvedilol and the calcium channel blocker verapamil significantly attenuated short-term BPV at both doses in SAD animals, and there were no differences between the drugs. Conversely, atenolol did not modify baseline s.d. values at either dose. Carvedilol and nebivolol significantly reduced the LF/HF ratio in SAD rats compared with the effects of atenolol and verapamil, suggesting the ability of the third generation b-blockers to reduce vascular sympathetic activity. In conclusion, third generation b-blockers induce a marked reduction in short-term BPV in SAD rats compared to atenolol. Moreover, the ability of carvedilol and nebivolol to reduce short-term BPV in SAD rats is equivalent to that of verapamil, suggesting that these b-blockers may have an additional beneficial effect through their control of short-term variability to a similar extent to calcium channel blockers.