Effect of baroreceptor denervation on the autonomic control of arterial pressure in conscious mice

Abstract

This study evaluated the role of arterial baroreceptors in arterial pressure (AP) and pulse interval (PI) regulation in conscious C57BL mice. Male animals, implanted with catheters in a femoral artery and a jugular vein, were submitted to sino-aortic (SAD), aortic (Ao-X) or carotid sinus denervation (Ca-X), 5 days prior to the experiments. After basal recording of AP, the lack of reflex bradycardia elicited by administration of phenylephrine was used to confirm the efficacy of SAD, and cardiac autonomic blockade with methylatropine and propranolol was performed. The AP and PI variability were calculated in the time and frequency domains (spectral analysis/fast Fourier transform) with the spectra quantified in low-(LF; 0.25-1 Hz) and high-frequency bands (HF; 1-5 Hz). Basal AP and AP variability were higher after SAD, Ao-X or Ca-X than in intact mice. Pulse interval was similar among the groups, whereas PI variability was lower after SAD. Atropine elicited a slight tachycardia in control mice but did not change PI after total or partial denervation. The bradycardia caused by propranolol was higher after SAD, Ao-X or Ca-X compared with intact mice. The increase in the variability of AP was accompanied by a marked increase in the LF and HF power of the AP spectra after baroreceptor denervation. The LF and HF power of the PI were reduced by SAD and by Ao-X or Ca-X. Therefore, both sino-aortic and partial baroreceptor denervation in mice elicits hypertension and a remarkable increase in AP variability and cardiac sympathetic tonus. Spectral analysis showed an important contribution of the baroreflex in the power of LF oscillations of the PI spectra. Both sets of baroreceptors seem to be equally important in the autonomic regulation of the cardiovascular system in mice.

Toll-like receptor 9 plays a key role in the autonomic cardiac and baroreflex control of arterial pressure

“…The propranolol-induced increase in PI is comparable to that observed in previous studies in mice (26,40,87). On the other hand, the parasympathetic contribution to resting HR has varied among studies, with reports of minimal (26,40,87), moderate (38), and substantial HR responses to atropine (78,88,100).…”

“…In the time domain, overall AP and PI variability were determined by the standard deviation of successive normal values (SDNN); the PI variability was also determined by the square root of the mean of the sum of the square of differences between adjacent PI values (RMSSD) (98a). In the frequency domain, spectral analysis was calculated using a fast Fourier transform (FFT) algorithm and integrated in two frequency bands: low (LF: 0.25 to 1 Hz) and high frequency (HF: 1 to 5 Hz), according to previous studies in our laboratory (87). Prior to spectral analysis, systolic AP and PI series were resampled to 10 Hz by cubic spline interpolation and divided into contiguous segments of 512 values, which overlapped by 50%.…”

Arterial Stiffening Provides Sufficient Explanation for Primary Hypertension

“…First, while numerous studies show that SAD does not lead to fixed hypertension, there certainly exist studies showing that it does (e.g. Machado and Brady [40], Rodrigues et al [41]). There is, however, consensus that SAD tends to cause a marked increase in pressure within the first hours/days.…”

Sex-Dependent Association between Heart Rate Variability and Pulse Pressure in Haemodialysis Patients

“…Chronic sympathetic overactivation results in decreased capacity of modulation and LF power, uremic peripheral neuropathy may disturb the autonomic reflex mechanisms and impaired baroreceptors may affect both spectral powers of HRV [14]. In particular, the interpretation of the LF/HF ratio should take into consideration that while the HF power corresponds to parasympathetic modulation, the LF power contains both sympathetic and parasympathetic components [15].…”