LIGHT-DARK DIFFERENCE IN ARTERIAL-PRESSURE VARIABILITY DURING REM-SLEEP IN THE RAT

We have observed mean arterial pressure (MAP) variability during rapid eye movement (REM) sleep and brain temperature (Tb) in the rat during both light and dark periods over 24 h. MAP was measured using a telem etric device with a computer data capture and analysis system. As mark ers of MAP variability, the maximum and coefficient of variation (CV%) of MAP during REM sleep were determined. The following results were o btained: (a) there was a light-dark difference in MAP during non-REM ( NREM) sleep and Tb during both NREM and REM sleep; (b) the increase of MAP in going from NREM to REM sleep in the light period was greater t han that in the dark period, whereas the increase of Tb in the light p eriod was not different from that in the dark period; (c) the maximum and CV% for MAP during REM sleep in the light period were greater than those in the dark period; (d) there was a negative correlation betwee n the average Tb and MAP CV% during REM sleep. We suggest that phasic fluctuation of MAP during REM sleep may be influenced, in part, by a f actor independent of sleep mechanisms.