Author(s): PASSAGLIA, J., MAIDA, K., VEIGA, A., SOUZA, H., Institution: UNIVERSITY OF SAO PAULO , Country: BRAZIL, Abstract-ID: 2517

INTRODUCTION:
Systemic arterial hypertension (SAH) is associated with cardiovascular autonomic alterations, including sympatho-vagal imbalance and reduced baroreflex sensitivity (BRS). Although pharmacological treatment reduces blood pressure (BP), its effects on autonomic modulation during aging remain inconsistent. Therefore, this experimental study investigated, in old male hypertensive rats, the effects of amlodipine alone or combined with aerobic physical training (APT) on hemodynamic and cardiac autonomic parameters.
METHODS:
Spontaneously hypertensive rats (SHR; N = 32) aged 52 weeks were divided into two groups (N = 16): vehicle-treated and amlodipine-treated (10 mg·kg⁻¹·day⁻¹) for 16 weeks. Half of each group (N = 8) underwent aerobic physical training (swimming) for 20 weeks. BP was assessed by tail-cuff plethysmography before (34th week of life) and at the end of the experimental protocol (72nd week). At the 72nd week, cardiovascular autonomic regulation was also evaluated through double pharmacological autonomic blockade using atropine and propranolol, heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS).
RESULTS:
All groups showed similar BP and heart rate (HR) values at baseline. At the end of the protocol, all groups treated with amlodipine and/or submitted to APT showed reduced BP values, whereas only the trained groups exhibited reduced HR. Double pharmacological blockade demonstrated that the trained groups—Vehicle (37 ± 13% vs. 22 ± 6%) and Amlodipine (45 ± 9% vs. 29 ± 5%)—showed increased vagal influence on HR compared to their respective sedentary groups. However, only the Vehicle group (311 ± 9 vs. 294 ± 7 bpm) showed a reduction in intrinsic pacemaker heart rate after double blockade. Spectral analysis of HRV revealed that trained groups showed reduced low-frequency oscillations (LF; 0.04–0.15 Hz) in normalized units and increased high-frequency oscillations (HF; 0.15–0.4 Hz). BPV analysis showed no significant differences among groups. Finally, trained groups exhibited increased BRS.
CONCLUSION:
Although amlodipine treatment reduced BP in old SHR, it did not appear to influence cardiovascular autonomic regulation. In contrast, the results obtained with APT highlight the fundamental role of this intervention as a countermeasure to the effects of SAH on cardiovascular autonomic regulation in the elderly.