Abstract.
We investigated the behavioral thermoregulation of heat-acclimated rats by measuring their selected ambient temperatures (T s). Rats kept in a light:dark cycle of 12:12 h were subjected to one of four different heat exposure regimes for 10 consecutive days; a constant ambient temperature (T a) of 32°C (CH), a T a of 32°C for 5 h daily in the latter half of the dark phase (IHF), a T a of 32°C for 5 h daily at a random time of day (IHR), or a constant T a of 24°C (control). After the heat exposure schedule, the rats were placed in a thermal gradient and their intra-abdominal temperature (T ab), T s and spontaneous activity were measured for 3 days. There were clear day–night variations of T ab and T s in all groups. The levels of T ab and T s of the CH rats were significantly higher than those of the IHF, IHR and control rats. The T ab and activity levels of the IHF rats were significantly lower than those of the IHR and control rats only in the latter half of the dark phase. The T s values of the IHF rats did not differ from those of the IHR and control rats. These results suggest that, after rats were constantly subjected to heat, heat-seeking behavior was induced so that the core temperature was maintained at a high level. However, when rats were acclimated to heat given for several hours at a fixed time daily, core temperature was lowered during the same time period of previous heat exposure in association with a depression of thermogenic behavior.
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Received after revision: 11 June 1999
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Sugimoto, N., Sakurada, S. & Shido, O. Selected ambient temperatures of rats acclimated to heat given on various schedules . Pflügers Arch – Eur J Physiol 438, 766–770 (1999). https://doi.org/10.1007/s004249900129
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DOI: https://doi.org/10.1007/s004249900129