Body temperature regulation in rats during exercise of various intensities at different ambient temperatures.

Abstract

We examined the relationship between body temperature, tail vasomotor response, and work intensity at different ambient temperatures in rats, using a treadmill and continuously measuring oxygen uptake during exercise. At an ambient temperature (Ta) of 24°C, rectal temperature (Tre) at the beginning of tail vasodilation during exercise increased in proportion to work intensity. After tail vasodilation Tre remained steady, and at the end of 30 min exercise Tre level was proportional to work intensity. At Ta of 14°C, Tre at the end of exercise was slightly higher than at 24°C, and was higher at higher work intensities. At Ta of 4°C, Tre rose slower during exercise than at higher Tas and even dropped at relatively low work intensities. Tail vasodilation did not occur in most cases. At Ta of 34°C, TCe rose continuously during exercise. These data indicate that body temperature of rats during exercise rises in proportion to work intensity, but the extent of body temperature rises differs according to Ta. Key words ; rectal temperature, tail vasomotor response, work intensity, ambient temperature, rat.Deep body temperature in man rises during exercise in proportion to work intensity, irrespective of ambient temperature (Ta) of 5 to 25°C (NIELSEN,1938). The physiological mechanism of this exercise-induced hyperthermia is not clear. Although man has been given detailed attention in many studies, methodological limitations have necessitated animal studies as well.The rat, extensively used as an experimental animal in acute and chronic studies, has made a great contribution to elucidate central nervous mechanism for thermoregulation. Since the rat, however, does not sweat or pant (ADOLF, 1947), and moreover cannot spread saliva effectively during exercise, how is body temperature of the rats during exercise influenced by work intensity and Ta? Although some reports have investigated the relationship between work intensity

Association between the increase in brain temperature and physical performance at different exercise intensities and protocols in a temperate environment

“…The dependence of hyperthermia level on exercise intensity was not observed for running mice (27), but it agrees with observations for exercising humans (28,29) and exercising rodents that had their abdominal or rectal temperature measured (25,30). That exercising mice present different physiological responses from other species was also reported in a recent investigation focusing on their running-induced ventilatory responses (31), which may lead ultimately to a distinctive pattern of evaporative heat loss from the respiratory tract.…”

“…This marked T brain increase was likely caused by animal handling (a stressful procedure required to insert the thermistor) and/or by the lower rate of heat loss compared with the rate of heat production generally observed at the beginning of exercise [cutaneous heat dissipation usually increases within 8 to 10 min of exercise under temperate conditions (15)]. Indeed, the former hypothesis helps to understand why the initial T brain increase was unspecific to the treadmill speeds studied, whereas the second hypothesis is supported by observations that a steady-state T core (rectal or abdominal) was only attained following the increase in tail skin temperature during low-intensity exercise (24,25). …”

Surprisingly low risk of overheating during digging in two subterranean rodents

“…The increase in body temperature during intensive physical activity is a common phenomenon in mammals (e.g., [12,22,23]). Aerobic heat production is a function of oxygen consumption; for each liter of oxygen, about 20 kJ of heat is produced [24].…”

Peer Review #2 of "Automatic analysis of treadmill running to estimate times to fatigue and exhaustion in rodents (v0.2)"

“…At room temperature, heat loss mechanisms have sufficient power to dissipate the heat 387 generated by exercise at relatively low power which was used in this study (Tanaka et al 1988). …”