Fig. 3: Longitudinal ECG recording reveals differential circadian regulation of SA and AV node function in mice.
From: Distinct circadian mechanisms govern cardiac rhythms and susceptibility to arrhythmia
A Rhythms in locomotor activity (LA, arbitrary units) and ECG-derived heart rate (HR), HRV, RR, QT, and PRseg parameters in mice (based on 5 days of recording; shading reflects + /− SEM; x axis black bar indicates dark phase; n = 10 mice). B–E Impact of LA and HR on ECG parameters. B Decreased LA during mid-night siesta (marked by an arrow in A) was accompanied by a significant decrease in RR and QT intervals, but not in PRseg duration (2-h siesta period (black) vs preceding 2 h of activity (blue); two-way RM ANOVA). C Periods of LA followed by >45 min of complete inactivity were isolated and aligned to the cessation of activity (time 0). RR (yellow), QT (blue), and to a lesser extent PRseg (orange) showed a significant response to the activity which decreased over subsequent inactivity (two-way RM ANOVA, Dunnet’s post hoc, difference from t = 40). D Transient bouts of LA (preceded and followed by inactivity) caused a significant response in RR and QT interval lengths, but not PRseg (two-way RM ANOVA, Dunnet’s post hoc, difference from t = −5). E Acute change in RR (across 5-min analysis bins) was mirrored by concordant changes in QT, but not PRseg. F Representative body temperature profile recorded across a 9-h advance of the LD cycle (data are double plotted; shaded regions indicate periods of darkness). G The 9-h phase advance led to profound separation in RR (black) and PRseg (orange) interval rhythms. H Mean RR and PRseg intervals measured across dark (green) and light (pink) phases the day prior to shift (day 0) and equivalent times on the day of the shift (day 1; two-way RM ANOVA, n = 11 mice). I Misalignment of RR and PRseg rhythms in response to the shift in LD cycles disrupts the normal temporal relationship of the two parameters. Data reflect group mean PRseg/RR on the day prior to shift (black) and the shift day (blue). All data presented as mean ± SEM. ns P > 0.05, *P < 0.05, **P < 0.01, ***P < 0.001. Source data and statistical details are provided as a Source Data File.
