Article date: March 2008
By: D Bedette, R A S Santos, M A P Fontes in Volume 153, Issue 5, pages 966-971
Background and purpose:
Studies have shown that the angiotensin II AT1 receptor antagonist, losartan, accentuates the hypotensive response in the orthostatic stress test (tilt) performed in anaesthetized rats. The same effect was not reported with other AT1 antagonists. The aim of this study was to re‐evaluate the effects of AT1 receptor blockade on the cardiovascular response to tilt in a model developed for conscious rats.
Experimental approach:
Rats (n=5–7 per group) were instrumented for infusion of drugs and recording of cardiovascular parameters and, after recovery, placed in a plastic tube positioned over the tilt board. The tilt test was conducted by raising the head side of the tilt board from horizontal position to 75° head up position for 15 min.
Key results:
Compared with control group (NaCl 0.9%, 1 ml kg−1), oral treatment with 1 mg kg−1 per day of losartan or telmisartan did not alter the blood pressure response during tilt. With the 10 mg kg−1 dose, both antagonists altered the blood pressure response during tilt (mean maximum changes −11±3 mm Hg; P<0.01). A post‐tilt hypotension was observed with both doses in losartan and telmisartan groups (−13±1 and −9±2 mm Hg, respectively; P<0.01).
Conclusions and implications:
The present results indicate that the effect of losartan on the cardiovascular reactivity to tilt shares a similar profile to that of other AT1 antagonists. Evidence discussed addresses the importance of using a conscious model for testing the influence of antihypertensive drugs on the cardiovascular reactivity to orthostatic challenges.
DOI: 10.1038/sj.bjp.0707652
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