Fig. 1.

Basal-state, intrinsic-state, and Δ (basal state- intrinsic state) comparison values at 20 °C and 30 °C in young and old mice of A mean heart rate (bpm), B time-domain parameter SDNN, C frequency-domain parameters categories (power spectral density), D non-linear domain parameters multi-scale entropy and Beta-slope, and E representative ECG tracings from young and old mice at 20 °C and 30 °C, respectively. Data is reported as means with standard error bars. Linear mixed effects models were used to examine age, temperature, and drug effects and interactions between effects while accounting for uneven group sizes and repeated measures