Core body temperature varies according to the time of exercise without affecting orexin-A production in the dorsal hypothalamus in male rats

• Published in: Journal of thermal biology Vol. 114; p. 103522
• Main Authors: Koumar, O.C., Martin, T., Bataille, A., Bulla, J., Crunel, V., Bouet, V., Freret, T., Boumediene, K., Bauge, C., Moussay, S., Dauphin, F., Bessot, N.
• Format: Journal Article
• Language: English; French
• Published: England Elsevier Ltd 01.05.2023; Pergamon Press ; Elsevier [1975-....]
• Subjects: Animals; Body Temperature - physiology; Body Temperature Regulation - physiology; Core body temperature; Dorsal hypothalamus; Hypocretin-1; Hypothalamus - metabolism; Life Sciences; Male; Orexins - metabolism; Physical activity; Rats; Rats, Wistar; Thermoregulation; Thermoregulation; Dorsal hypothalamus; Hypocretin-1; Physical activity; Core body temperature
• ISSN: 0306-4565; 1879-0992
• DOI: 10.1016/j.jtherbio.2023.103522

Physical exercise differentially increases body temperature according to the time of day, which shows the importance of circadian rhythm in thermal regulation. Given its contribution in central pathways involved in thermoregulation, orexin A could play a role in the regulation of core body temperature during and after exercise. To test this hypothesis, we assessed the effect of exercise, performed at two times of day, on core temperature and on the amount of orexin A in the production zone, i.e., the dorsal hypothalamus. Forty-nine male Wistar rats underwent forced treadmill exercise during the HG phase and HL phase of core temperature. Basal core temperature was recorded continuously for 48 h by implanted telemetric sensors in 11 rats. Regulation of core temperature during exercise (20 min) and after each exercise (60 min) was modeled with a modified logistic-type function. During HG exercise, core temperature curve reached a significantly higher maximum (asymptote: +0.70 ± 0.10 °C) and took longer to attain the strongest inclination of the core temperature regulation curve (Xmid: 3.46 ± 0.72 min). After HG exercise, time of recovery was significantly longer than after HL exercise. In male rats, thermoregulatory response to acute physical exercise was influenced by the time of day. There was no effect of either physical activity or time of day on the level of orexin A in the dorsal hypothalamus. Our results suggest that orexin A in the dorsal hypothalamus is not involved in the effects of physical exercise on thermoregulation. •The rat's thermoregulation during physical activity differs depending on the time of day.•The increase in core body temperature is highest during the activity period.•Diurnal difference in core body temperature is persistent throughout the 20 min of exercise.•- The level of orexin A in the dorsalhypothalamus is not changed in all physical exercise conditions.