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Angiotensin‐(1‐7) antagonist into the CVLM improves baroreflex bradycardia in renovascular hypertensive rats
Author(s) -
CampagnoleSantos Maria J,
Cangussu Luiza M,
Machado Raquel P,
Ferreira Patricia M,
Silva Marcelo E,
Santos Robson AS,
Alzamora Andreia C
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1169.15
Subject(s) - baroreflex , bradycardia , mean arterial pressure , blood pressure , phenylephrine , heart rate , medicine , microinjection , anesthesia , cardiology
We have shown that Ang‐(1‐7) at the caudal ventrolateral medulla (CVLM) induces a decrease in the baroreflex bradycardia (BRS) in normotensive rats. In this study we evaluated the changes in mean arterial pressure (MAP), heart rate (HR) and BRS induced by CVLM microinjection of the Ang‐(1‐7) antagonist, A779, in normotensive (Sham) and renal hypertensive (2K1C) rats. Blood pressure was recorded by Powerlab system and BRS was estimated by the ratio between changes in HR (as pulse interval) and changes in MAP induced by phenylephrine. CVLM microinjection of A779 produced decreases in MAP in 2K1C (−12 ± 3 mmHg; n=6; Baseline MAP=141 ± 6 mmHg; n=7) in contrast to that observed in Sham (−5 ± 2 mmHg; Baseline MAP= 108 ± 3 mmHg; n=8). No significant changes in HR were observed in Sham or 2K1C. A779 injection significantly increased baroreflex bradycardia in 2K1C (0.44 ± 0.05 ms/mmHg, n=7 vs 0.24 ± 0.03 ms/mmHg, n=7; before). However, A779 did not alter baroreflex bradycardia in Sham rats (0.35 ± 0.04 ms/mmHg, n=7 vs 0.40 ± 0.02 ms/mmHg, n=7; before). These data suggest that increased levels of Ang‐(1‐7), at least in the CVLM, may contribute to the low sensitivity of the baroreflex control of heart rate in renovascular hypertensive rats. Support: CNPq, FAPEMIG, PRONEX, REDE‐TOXIFAR‐UFOP.