(A) Heart rate is plotted hourly (left panel) and averaged across the light, dark, and 24-hour phases (right panel). Shaded areas indicate the dark phase (control n=7, renin-bNull mice n=8). (B) Relative low frequency, high frequency (LF/HF) ratio derived from power spectral analysis of heart rate variability (n=7 per group). (C–D) Heart rate responses to i.p. injection of propranolol (C) or atropine (D) (n=7 per group). (E) Baroreflex gain derived from Sequence method (n=7 per group). *, P<0.05 vs control.