Autonomic cardiovascular control in conscious mice

Abstract

Autonomic cardiovascular control was characterized in conscious, chronically catheterized mice by spectral analysis of arterial pressure (AP) and heart rate (HR) during autonomic blockade or baroreflex modulation of autonomic tone. Both spectra were similar to those obtained in humans, but at approximately 10x higher frequencies. The 1/f relation of the AP spectrum changed to a more shallow slope below 0.1-0.2 Hz. Coherence between AP and HR reached 0.5 or higher below 0.3-0.4 Hz and also above 2.5 Hz. Muscarinic blockade (atropine) or beta-adrenergic blockade (atenolol) did not significantly affect the AP spectrum. Atropine reduced HR variability at all frequencies, but this effect waned above 1 Hz. beta-Adrenergic blockade (atenolol) slightly enhanced the HR variability only above 1 Hz. alpha-Adrenergic blockade (prazosin) reduced AP variability between 0.05 and 3 Hz, most prominently at 0. 15-0.7 Hz. A shift of the autonomic nervous tone by a hypertensive stimulus (phenylephrine) enhanced, whereas a hypotensive stimulus (nitroprusside) depressed AP variability at 1-3 Hz; other frequency ranges of the AP spectrum were not affected except for a reduction below 0.4 Hz after nitroprusside. Variability of HR was enhanced after phenylephrine at all frequencies and reduced after nitroprusside. As with atropine, the reduction with nitroprusside waned above 1 Hz. In conclusion, in mice HR variability is dominated by parasympathetic tone at all frequencies, during both blockade and physiological modulation of autonomic tone. There is a limitation for further reduction but not for augmentation of HR variability from the resting state above 1 Hz. The impact of HR on AP variability in mice is confined to frequencies higher than 1 Hz. Limits between frequency ranges are proposed as 0.15 Hz between VLF (very low frequency range) and LF (low frequency range) and 1.5 Hz between LF and HF (high frequency range).

Exercise training changes autonomic cardiovascular balance in mice

“…The presence of the bradycardia is important because it documents the effectiveness of the training protocol. In this context, the HR values observed in the sedentary mice are similar to those previously observed in this and other mouse strains (14,21,27).…”

Rosuvastatin Decreases Caveolin-1 and Improves Nitric Oxide–Dependent Heart Rate and Blood Pressure Variability in Apolipoprotein E −/− Mice In Vivo

“…The bandwidth characteristic of each component varies among animal species and was recently determined in mice. 10,14 We independently validated the influence of the parasympathetic component and of the NO pathway on our spectra using acute pharmacological inhibition with atropine and an NOS inhibitor, respectively. In control mice, we found that HR variability in the HF band was abrogated by atropine ( Figure 3B), confirming its dependence on a functional parasympathetic system.…”

“…The area under the curve was calculated for the very-low-frequency (VLF: 0.05 to 0.4 Hz), low-frequency (LF: 0.4 to 1.5 Hz), and highfrequency (HF: 1.5 to 5.0 Hz) bands, as previously defined in the mouse species. 10,14 Spectral variability at each bandwidth was normalized to the total spectral area.…”

Weight Loss–Associated Induction of Peroxisome Proliferator–Activated Receptor-α and Peroxisome Proliferator–Activated Receptor-γ Correlate With Reduced Atherosclerosis and Improved Cardiovascular Function in Obese Insulin-Resistant Mice

“…The area under the curve was calculated for the very-low-frequency (VLF, 0.05 to 0.4 Hz), low-frequency (LF, 0.4 to 1.5 Hz), and high-frequency (HF, 1.5 to 5.0 Hz) bands as previously defined in the mouse. [17][18][19] Spectral variability at each bandwidth was normalized to the total spectral area.…”