RESTRAINING EFFECTS OF LOSARTAN ON BLOOD PRESSURE AND HEART RATE VARIABILITY INDUCED BY STRESS

Summary— The effects of chronic treatment with losartan on blood pressure (BP) and heart rate (HR) variability responses during air‐jet stress were studied in WKY and SHR. In untreated animals, air‐jet stress induced an increase in systolic BP (SBP) (9 ± 2 mmHg for WKY and 8 ± 2 mmHg for SHR) and HR (56 ± 19 bpm for WKY and 76 ± 8 bpm for SHR). These changes were accompanied by an increase of the mid frequency (0.2–0.6 Hz, MF) component of HR in WKY (183%) and by an increase of the MF component of SBP in SHR (65%). Chronic suppression of the renin‐angiotensin system (RAS) by losartan reduced resting BP only in SHR (‐20 mmHg for SBP) without affecting HR and did not modify the resting MF components of BP and HR. This pretreatment did not alter the BP response in WKY to stress but impaired it in SHR. In both strains, treatment with losartan abolished all BP and HR variability changes, whereas the tachycardia response was unaltered. Losartan caused inhibition of BP and HR variability changes in response to stress in WKY and SHR. We provided evidence for the importance of the angiotensin II‐sympathetic interaction in the BP and HR variability responses to a stressful environment.