Vigilance state episodes and cortical temperature in the Djungarian hamster: the influence of photoperiod and ambient temperature

Abstract

 The electroencephalogram, electromyogram and cortical temperature (T _CRT) were recorded in seven Djungarian hamsters adapted to a short photoperiod at 16°C ambient temperature (T_A; SP16). A baseline day was followed by 4 h sleep deprivation (SD) and 20 h recovery. The analysis included data obtained in earlier experiments at 22°C T_A in a long (LP22) and short photoperiod (SP22). In all three conditions the changes in T _CRT during vigilance state episodes were a function of episode duration and, for waking and non-rapid eye movement (NREM) sleep, of T _CRT at episode onset. The increase in T _CRT during REM sleep became progressively larger from LP22 to SP22 to SP16. After SD the mean T _CRT decreased below baseline in the LP22 and stayed above baseline in the SP22. This difference in the effect of SD on T _CRT was reflected in its increase during REM sleep, which was attenuated during recovery in LP22, but was enhanced in SP22. The time course of T _CRT during NREM sleep or waking episodes was unaffected by SD. Therefore, the overall difference in T _CRT between baseline and recovery in the LP22 and SP22 is due to changes in the increase in T _CRT during REM sleep.