Patterns of cardiovascular variability after long-term sino-aortic denervation in unanesthetized adult rats

Figures

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  Figure 1. Five-minute segments of MBP and IBI series in a control rat and in a SAD rat at day 1, at day 3 and at 7 months from denervation. MBP variability, with blood pressure sudden reductions, clearly increases immediately after SAD and remains high thereafter. On the other hand, IBI variability, that decreases immediately after SAD, thereafter increases. The increase in IBI variability is sustained by sudden IBI prolongations that coincide with blood pressure reductions.

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  Figure 2. Comparison of MBP power spectra in the control group (black) vs. SAD groups 1 day (red), 3 days (light blue) and 7 months (green) after denervation. Upper panels: geometric mean ± geometric standard error, plotted in log-log scale; lower panels: Student t statistics for each spectral line, with 10%, 5% and 1% statistical thresholds (dashed horizontal lines). At frequencies where the Student t is above the threshold, the difference between groups is statistically significant. Spectral lines below 0.1 Hz have greater amplitude in SAD rats than in controls at any time from denervation; spectral lines above 1 Hz are greater in SAD rats, the difference being more pronounced in the acute than in the chronic phases. Interestingly, a spectral peak in control rats at 0.38 Hz (i.e., in the LF band) disappears in SAD rats.

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  Figure 3. Comparison of IBI power spectra in the control group (black) vs. SAD groups 1 day (red), 3 days (light blue) and 7 months (green) after denervation. Upper panels: geometric mean ± geometric standard error, in log-log scale; lower panels: Student t statistics (see also Fig. 2). Compared to controls, the spectrum is significantly lower one day after SAD. Thereafter the power of the spectrum of SAD rats increases to become significantly higher 7 months after SAD almost at all the frequencies.

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  Figure 4. Coherency Modulus after Fisher z-transform in the control group (black) vs. SAD groups 1 day (red), 3 days (light blue) and 7 months (green) after denervation. Upper panels: mean ± standard error. Lower panels: Student t statistics (see also Fig. 2). The coherency modulus in the LF band is lower after SAD, the difference with controls being highly significant 3 days and 7 months after SAD; by contrast, the coherency modulus in the ULF band is high in all SAD groups, similarly to controls.

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  Figure 5. SBP-IBI phase in the control group (black) and in SAD groups 1 day (red), 3 days (light blue) and 7 months (green) after denervation. Circular mean and ±circular standard error: note the high uncertainty of estimates at frequencies where the coherency modulus is low (Fig. 4); in the ULF band, where it is high, the phase is close to −π/2 [rad] in controls, and to −π [rad] in all SAD groups.

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  Figure 6. Ten-minute segments of MBP and IBI series in a SAD rat 7 months after denervation, in baseline and during a stressful stimulus. Note that even if the stressful stimulus may modify the general behaviour of the rat, the pattern of ULF variability during stress is similar to that of the baseline condition, i.e., with MBP sudden reductions and IBI prolongations that coincide with blood pressure reductions. In addition, the stressful stimulus increases the MBP level and the amplitude of MBP faster LF oscillations.

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  Figure 7. Generation of a couple of surrogate SBPS-IBIS series from original SBP-IBI series. Left panels: example of T = 10 minute segment of SBP and IBI time series recorded in a control rats; right panels: corresponding surrogate series, obtained by exchanging first and second half of the IBI series.

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  Figure 8. SBP-IBI Coherency Modulus after Fisher z-transform in the control group (black) vs. the corresponding surrogate series (blue). Upper panels: mean and tolerance limits as range between 10th and 90th percentile; the dotted horizontal line indicates the Cth threshold. Lower panels: Student t statistics for the paired comparison.