Effect of ambient temperature on arterial pressure variability during sleep in the rat.

Changes in mean arterial pressure (MAP) and heart rate (HR) during sleep were recorded at three ambient temperatures (Ta: 16, 22 and 28 degrees C). MAP and HR during sleep increased with lowering of Ta. The increase in MAP during the transition from NREM to REM sleep was decreased by lowering the Ta. At 28 degrees C, the average HR increased in going from NREM to REM sleep, while, at 16 degrees C, it decreased. The coefficient of variation (CV%) of the MAP during REM sleep decreased as the Ta was lowered, while that seen during NREM sleep was unchanged. This study suggests that Ta has a greater effect than sleep stage on the MAP and HR, and that MAP variability during REM sleep is greater at higher Ta.