Thermopreferendum of the rat: inter- and intra-subject variabilities

The thermopreferendum of male hooded rats was studied in a temporal thermal gradient. The preferred ambient temperature was found to be approximately 19 degrees C. In addition to the thermopreferendum, three other physiological functions (resting body temperature, daily food intake, and daily ambulatory activity) were each measured in eight rats for 8 days. Overall variability of the thermopreferendum data was higher than that of body temperature and food intake data but lower than the variability of ambulatory activity data. Coefficients of inter- and intrasubject variabilities were computed for each of the four variables. Inter-subject variability was equivalent in all variables, but intrasubject variability was smaller for thermopreferendum and activity than for food intake and core temperature. The thermopreferendum of 19 degrees C is consistent with previously published results but inconsistent with the available data on the thermoneutral zone of the rat (27-28 degrees C). The cause of this inconsistency remains to be determined.