Changes in thermal preference, sleep–wakefulness, body temperature and locomotor activity of rats during continuous recording for 24 hours

Abstract

This study was aimed at correlating diurnal changes in thermal preference of rats with their body temperature ( T b), sleep–wakefulness (S–W) and locomotor activity (LMA). Electroencephalogram (EEG), electromyogram (EMG), electrooculogram (EOG) and T b were recorded by telemetry, while an activity monitor measured LMA and thermal preference. A special environmental chamber, which was designed and fabricated, enabled for the first time, simultaneous measurement of thermal preference, along with S–W and T b. S–W, thermal preference and LMA were recorded continuously in six adult male Wistar rats, for 24 h, for 3 days, and T b with thermal preference and LMA were recorded for another 3 days. LMA and T b were higher at night than during day. The rats slept less during the night time. Increased frequency of sleep episodes contributed towards increased sleep during day time. They preferred an ambient temperature ( T amb) of 24 °C at night and 27 °C during the day. Though the preference for higher T amb during day time coincided with increased sleep, the rats did not move over to higher T amb prior to the onset of sleep episodes. Though the diurnal alterations in sleep, T b and LMA were similar to those reports from animals kept in constant T amb, the day–night variation of paradoxical sleep (PS) was exaggerated when the rats selected their own preferred T amb.