Evaluation of baroreflex control of heart rate in renovascular hypertensive mice

• Published in: Canadian journal of physiology and pharmacology 2007-08, Vol.85 (8), p.761-766
• Main Authors: Peotta, Veronica A, Gava, Agata L, Vasquez, Elisardo C, Meyrelles, Silvana S
• Format: Article
• Language: English
• Subjects: Animals; Atenolol; Atropine; Autonomic nervous system; Baroreceptors; Baroreflex; baroréflexe; Biological and medical sciences; Blood Pressure; Bradycardia; Cardiac arrhythmia; cardiac hypertrophy; Care and treatment; Catheters; Control; Experiments; Fundamental and applied biological sciences. Psychology; Heart beat; Heart Rate; Hypertension; hypertension rénovasculaire; Hypertension, Renovascular - physiopathology; hypertrophie cardiaque; Kidneys; Laboratory animals; Male; Measurement; Mice; Mice, Inbred C57BL; Phenylephrine; Physiological aspects; Reflexes; Regression analysis; renovascular hypertension; Rodents; Sensitivity analysis; Sodium nitroprusside; Sympathetic nervous system; sympathetic tone; Tachycardia; tonus sympathique; tonus vagal; vagal tone; Vagus nerve; Variance analysis; Veins & arteries; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/Y07-067

The objective of the present study was to evaluate the baroreflex and the autonomic control of heart rate (HR) in renovascular hypertensive mice. Experiments were carried out in conscious C57BL/6 (n = 16) mice 28 days after a 2-kidney 1-clip procedure (2K1C mice) or a sham operation (sham mice). Baroreflex sensitivity was evaluated by measuring changes in heart rate (HR) in response to increases or decreases in mean arterial pressure (MAP) induced by phenylephrine or sodium nitroprusside. Cardiac autonomic tone was determined by use of atropine and atenolol. Basal HR and MAP were significantly higher in 2K1C mice than in sham mice. The reflex tachycardia induced by decreases in MAP was greatly attenuated in 2K1C mice compared with sham mice. Consequently, the baroreflex sensitivity was greatly decreased (2.2 ± 0.4 vs. 4.4 ± 0.3 beats·min -1 ·mmHg -1 ) in hypertensive mice compared with sham mice. The reflex bradycardia induced by increases in MAP and the baroreflex sensitivity were similar in both groups. Evaluation of autonomic control of HR showed an increased sympathetic tone and a tendency to a decreased vagal tone in 2K1C mice compared with that in sham mice. 2K1C hypertension in mice is accompanied by resting tachycardia, increased predominance of the cardiac sympathetic tone over the cardiac vagal tone, and impairment of baroreflex sensitivity.