Elevated body temperature in female rats after exercise

Area of Science:

• Physiology
• Animal Behavior
• Thermoregulation

Background:

• Sedentary Sprague-Dawley rats exhibit diurnal body temperature (Tb) variations, peaking in the dark phase and troughing in the light phase.
• Normal Tb ranges from 36.0°C (light) to 38.1°C (dark).

Purpose of the Study:

• To investigate the effect of voluntary exercise on body temperature regulation in rats.
• To determine if sustained exercise can alter the thermoregulatory set-point.

Main Methods:

• Telemetry was used to measure body temperature (Tb) in Sprague-Dawley rats under different housing conditions.
• Rats were housed in standard cages (sedentary) or cages with activity wheels (exercising).
• Experimental groups experienced cycles of wheel-open (WO) and wheel-locked (WL) conditions to isolate exercise effects.

Main Results:

• Rats housed in activity wheels showed increased mean peak Tb (39.5°C) during the dark phase and elevated mean trough Tb (36.5°C) during the light phase.
• During wheel-locked periods, Tb levels returned to sedentary control values, indicating exercise-dependence.
• Repeated cycles of wheel access and locking demonstrated rapid Tb adjustments, supporting a direct link between exercise and Tb regulation.

Conclusions:

• Steady, voluntary exercise, particularly during the active (dark) phase, leads to an upward resetting of the thermoregulatory set-point.
• This exercise-induced set-point shift influences body temperature during both activity and rest periods.
• The findings support the hypothesis that sustained physical activity can modify central thermoregulatory control mechanisms.