Abstract
Baroreflex dysfunction is a diffuse chronic condition that is expected to be followed by a profound loss of organization of BP and HR variability. Nevertheless, long-term effects of baroreflex withdrawal are still debated. Aim of our work was to study BP and HR changes long term after sino-aortic denervation (SAD). Inter-beat-interval (IBI) and intra-arterial BP were recorded beat-by-beat in 43 Wistar-Kyoto rats (Controls, n = 33; SAD rats, n = 10). Power spectra were calculated in controls and in SAD rats within three days and at seven months from denervation. Compared to controls, chronic SAD rats showed 1) similar mean BP (control vs SAD: 95 ± 16 vs 87 ± 22 mmHg) and IBI (171 ± 22 vs 181 ± 15 ms) values, 2) dramatically higher values of BP variance (12 ± 2 vs 64 ± 2 mmHg2, p < 0.01) and of ultra- (ULF) and very-low-frequency (VLF) BP oscillations, 3) dramatically higher values of IBI variability (24 ± 2 vs 71 ± 4 ms2, p < 0.01) and of ULF-IBI oscillations that were synchronized with BP oscillations. Chronic SAD rats reveal a marked change in the pattern of cardiovascular variability characterized by the appearance of synchronized slower oscillations of BP and HR. The cardiovascular system, therefore, retains a high level of organization despite the absence of a reflex control mechanism.
Highlights
The baroreceptor reflex plays a crucial role in the preservation of cardiovascular homeostasis as demonstrated by the striking increase in blood pressure (BP) variability that follows sino-aortic denervation (SAD) in animals[1,2,3,4]
Three days after SAD, MBP was significantly higher in the denervated rats, but it subsequently showed a decrease and seven months after SAD its value was similar in the denervated and in the control animals; inter-beat interval (IBI) was significantly shorter one day after SAD compared to control rats, but it subsequently increased and seven months after SAD it was similar to the value of the control animals (Table 1)
MBP variance was strikingly higher in SAD than in control rats at any time from SAD
Summary
The baroreceptor reflex plays a crucial role in the preservation of cardiovascular homeostasis as demonstrated by the striking increase in blood pressure (BP) variability that follows sino-aortic denervation (SAD) in animals[1,2,3,4]. As baroreflex dysfunction is a diffuse condition affecting ageing, deconditioning and different diseases (like hypertension, heart failure, diabetes mellitus, coronary disease, obesity and Parkinson’s disease)[5] and as changes in cardiovascular patterns could have consequences on prognosis[6,7,8,9], the chronic effects of baroreflex dysfunction on both BP and HR should be carefully investigated[5]. It is still not clear whether and to what extent baroreflex withdrawal affects BP and HR in the long term. The * and ** indicate differences vs. controls significant at p < 5% and p < 1% respectively by unpaired t-test after logtransformation for variance, by Mann Whitney U test for the respiratory rate
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