Autonomic Nervous System Adaptation and Circadian Rhythm Disturbances of the Cardiovascular System in a Ground-Based Murine Model of Spaceflight

Figures

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  Figure 1. Schematic representation of the experimental design.

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  Figure 2. Effects of HU on food, water intake and body weight. (a) Food and (b) water intake was averaged daily during basal state (C-1, white box), during HU (HU1 to HU5, black box), and during recovery (R+1 and R+2, grey box). Data were measured 24 h, at 10 a.m. the next day (n = 11 mice). * p < 0.05, ** p < 0.01 and *** p < 0.001 vs. C-1. (c) Body weight was measured before unloading (control, white bar), at the reloading (unloading, black bar) and after 2 days of recovery (recovery, grey bar). Body weight values were expressed as mean ± SD (n = 11 mice). ** p < 0.01 and *** p < 0.001 vs. control.

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  Figure 3. Ten-day continuous recordings of MBP, HR, locomotor activity, and subcutaneous temperature. Histograms representing day averaged data for each measure factor illustrating the values of (a) mean blood pressure, (b) heart rate, (c) locomotor activity, and (d) subcutaneous temperature. All data are expressed as 24 h mean ± SD (n = 8 mice). ** p < 0.01; *** p < 0.001 vs. C-1.

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  Figure 4. Time-domain analysis before (C-1), during unloading (HU1 to HU5) and recovery (R+1 and R+2). (a) Standard Deviation of NN intervals (SDNN) and (b) Root Mean Square of Successive R-R Interval Difference (RMSSD) were determined for 3 min mean triplicates, 20 h after each condition, between 8–10 am the next day. Inset: control (C-1, white bar), 5 days of unloading (HU1 to HU5, black bar) and 2-days recovery (R+1 and R+2, grey bar). Values are expressed as mean ± SD (n = 7 mice). * p < 0.05 and ** p < 0.01 vs. C-1.

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  Figure 5. Frequency-domain analysis before (C-1), during unloading (HU1 to HU5) and recovery (R+1 and R+2). (a) low frequency (LF), (b) high frequency (HF), and (c) sympathovagal balance (LF/HF ratio) were determined for 3 min mean triplicates, 20 h after each condition, between 8–10 a.m. the next day. Inset: control (C-1, white bar), 5 days of unloading (HU1 to HU5, black bar) and 2-days recovery (R+1 and R+2, grey bar). Values are expressed as mean ± SD (n = 7 mice).

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  Figure 6. Baroreflex sensitivity (BRS) before (C-1), during unloading (HU1 to HU5) and recovery (R+1 and R+2). Inset: control (C-1, white bar), 5 days of unloading (HU1 to HU5, black bar) and 2-days recovery (R+1 and R+2, grey bar). Values are expressed as mean ± SD for n = 7 mice. * p < 0.05 and ** p < 0.01 vs. C-1.

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  Figure 7. Locomotor activity changes during the unloading and recovery period. (a) Mean (black full curve) and median (black dotted curve) variations of locomotor activity were represented during 3 days of control (C-3 to C-1, white circle), 5 days of unloading (HU1 to HU5, black circle) and 2 days of recovery (R+1 and R+2, grey circle). White and grey bars indicate 12/12-h light (LC) and dark (DC) periods (7-7), respectively. Curves are smoothed, grey area represents the confidence interval (n = 8 mice). (b) Box plot showing locomotor activity during control (white box), unloading (black box) and recovery (grey box) periods for LC and DC (n = 8 mice).

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  Figure 8. Subcutaneous and central temperature variations. (a) Mean (purple full curve) and median (purple dotted curve) variations of subcutaneous temperature were represented during 3 days of control (C-3 to C-1, white circle), 5 days of unloading (HU1 to HU5, black circle) and 2 days of recovery (R+1 and R+2, grey circle). White and grey bars indicate 12/12-h light (LC) and dark (DC) periods (7-7), respectively. Curves are smoothed, grey area represents the confidence interval (n = 8 mice). (b) Box plots showing subcutaneous (n = 8 mice) and (c) central (n = 6 mice) temperature variations for control (white box), unloading (black box) and recovery (grey box) for LC and DC.

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  Figure 9. Arterial blood pressure changes before, during HU and recovery. (a) Mean variations of systolic (SBP, red full curve) and diastolic (DBP, red dotted curve) blood pressure were represented during 3 days of control (C-3 to C-1, white circle), 5 days of unloading (HU1 to HU5, black circle) and 2 days of recovery (R+1 and R+2, grey circle). White and grey bars indicate 12/12-h light (LC) and dark (DC) periods (7-7), respectively. Curves are smoothed, grey area represents the confidence interval (n = 8 mice). (b) SBP and (c) DBP box plots for control (white box), unloading (black box) and recovery (grey box) periods LC and DC.

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  Figure 10. Heart rate responses before, during HU and recovery. (a) Heart rate (HR, blue curve) represented 3 days of control (C-3 to C-1, white circle), 5 days of unloading (HU1 to HU5, black circle) and 2 days of recovery (R+1 and R+2, grey circle). White and grey bars indicate 12/12-h light (LC) and dark (DC) periods (7-7), respectively. Curves are smoothed, grey area represents confidence interval (n = 8 mice). (b) Box plot of HR for control (white box), unloading (black box) and recovery (grey box) periods LC and DC.