Autonomic mechanisms underpinning the stress response in borderline hypertensive rats

Abstract

This study investigates blood pressure (BP) and heart rate (HR) short-term variability and spontaneous baroreflex functioning in adult borderline hypertensive rats and normotensive control animals kept on normal-salt diet. Arterial pulse pressure was recorded by radio telemetry. Systolic BP, diastolic BP and HR variabilities and baroreflex were assessed by spectral analysis and the sequence method, respectively. In all experimental conditions (baseline and stress), borderline hypertensive rats exhibited higher BP, increased baroreflex sensitivity and resetting, relative to control animals. Acute shaker stress (single exposure to 200 cycles min-1 shaking platform) increased BP in both strains, while chronic shaker stress (3-day exposure to shaking platform) increased systolic BP in borderline hypertensive rats alone. Low- and high-frequency HR variability increased only in control animals in response to acute and chronic shaker (single exposure to restrainer) stress. Acute restraint stress increased BP, HR, low- and high-frequency variability of BP and HR in both strains to a greater extent than acute shaker stress. Only normotensive rats exhibited a reduced ratio of low- to high-frequency HR variability, pointing to domination of vagal cardiac control. In borderline hypertensive rats, but not in control animals, chronic restraint stress (9-day exposure to restrainer) increased low- and high-frequency BP and HR variability and their ratio, indicating a shift towards sympathetic cardiovascular control. It is concluded that maintenance of BP in borderline hypertensive rats in basal conditions and during stress is associated with enhanced baroreflex sensitivity and resetting. Imbalance in sympathovagal control was evident only during exposure of borderline hypertensive rats to stressors.

Impairment on cardiovascular and autonomic adjustments to maximal isometric exercise tests in offspring of hypertensive parents

“…3,17 Furthermore, a study using an animal model has provided direct confirmation that stress exposure plays a causal role in the pathogenesis of hypertension. 18 We observed increased HR in the first minute and after MST in relation to the HR at rest only in the OH group. Previous studies have also demonstrated that offspring of hypertensive parents submitted to an Arithmetic Test or to an Cold Pressor Test presented increased cardiovascular responses.…”

(–)-Epicatechin Reduces the Blood Pressure of Young Borderline Hypertensive Rats During the Post-Treatment Period

“…However, young SHR are not a suitable model for representing essential prehypertension in adulthood due to the early onset of fully developed hypertension (i.e., systolic BP over 140 mm Hg) before reaching adulthood (~12 weeks of age) [10]. A more appropriate genetic model of essential prehypertension consists of borderline hypertensive rats (BHR), which were obtained by the mating of female SHR and male normotensive Wistar-Kyoto (WKY), resulting in a systolic BP of approximately 140 mm Hg in the adulthood stage [11,12].…”

On Consistency of Cross-Approximate Entropy in Cardiovascular and Artificial Environments

“…During the experiments, the animals were exposed to two types of stress: shaker stress, with rats positioned on a platform shaking at 200 cycles/min, and restraint stress, with rats placed in a Plexiglas restrainer tube (ID 5.5 cm with pores) in the supine position, with a detailed description given in [24]. These data were already used for other research purposes [20,24,25]. The duration of records in baseline, restraint stress, and shaker stress was 20 minutes, 60 minutes, and 20 minutes, respectively.…”