Temporal Dynamics of Cardiovascular, and Thermoregulatory Homeostasis in Male and Female Mice

Objective: The autonomic nervous system acts as a regulator to coordinate cardiovascular, thermoregulatory, and other homeostatic functions in our body. While we know that these systems work together, we have never seen exactly how blood pressure, heart rate, and core body temperature dance with each other in real-time. Here, we reveal this hidden choreography and uncover surprising differences between male and female mice. Hypothesis: Core body temperature, traditionally considered a stable physiological parameter, undergoes rapid minute-to-minute fluctuations. These previously unrecognized dynamic changes raise fundamental questions about underlying mechanisms. We hypothesize that these swift temperature adjustments are driven by rapid changes in cardiovascular parameters, with blood pressure and heart rate acting as early signals in the body's thermoregulation. METHODOLOGY: Six adult wild-type male and female mice were surgically implanted with bipotential (electrocardiography and blood pressure) telemetry devices (DSI, PhysioTel HD-X11) to continuously monitor mean arterial blood pressure (MAP), heart rate (HR) and core body temperature (Tb) under thermoneutral conditions. Mice were housed in a 12-hour light:12-hour dark cycle with ad libitum food access, and data was collected for 10-second averages over 48 hours. Cross-correlation analysis was performed before and after removing the 24-hour rhythm component using LOESS regression. Results: Cross-correlation analysis revealed strong coupling among all three physiological parameters, with MAP-HR showing the highest correlation (males: 0.87, females: 0.80), followed by MAP-Tb (males: 0.76, females: 0.75) and HR-Tb (males: 0.78, females: 0.80). After detrending to remove circadian influences, MAP-HR correlations remained robust (males: 0.83, females: 0.74), while MAP-Tb (males: 0.69, females: 0.65) and HR-Tb (males: 0.69, females: 0.75) moderately decreased. This detrending approach helped distinguish between the physiological coupling and relationships independent of circadian rhythms. Cross correlations between MAP and HR showed no lag and a strong correlation in both original and detrended signals, serving as a positive control. With 24-hour rhythm, MAP led Tb by 7.0 ± 1.9 minutes in males and 8.6 ± 1.8 minutes in females, while HR preceded Tb by 5.7 ± 1.3 and 6.1 ± 1.0 minutes, respectively. These temporal relationships persisted after detrending (MAP-Tb: males 6.9 ± 1.9, females 8.4 ± 1.8 minutes; HR-Tb: males 5.6 ± 1.3, females 6.1 ± 1.0 minutes). Females consistently showed longer lags than males, and MAP maintained a longer lead over Tb compared to HR. Conclusion: The maintained MAP-HR correlation after detrending, contrasted with reduced temperature correlations, suggests that cardiovascular coupling operates independently of circadian rhythms, while temperature relationships maybe partially rhythm-dependent. This rapid linear lead-lag relationship between cardiovascular parameters, and Tb reveals a novel temporal hierarchy in physiological regulation. This work is supported by the National Heart Lung and Blood Institute, R01HL172813, and R01HL153042 grant to Prof. Brian P. Delisle. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.