SLEEP-DEPRIVATION IN THE RAT AT DIFFERENT AMBIENT-TEMPERATURES - EFFECT ON SLEEP, EEG SPECTRA AND BRAIN TEMPERATURE

To investigate the relationship between thermoregulation and sleep reg ulation, rats were sleep-deprived for 3 hours at two different ambient temperatures. Sleep deprivations (SD) were performed at 23-degrees-C (SD-23) and at 32-degrees-C (SD-32) in the beginning of the 12-h light period in animals chronically implanted with ECoG and EMG electrodes, and with epidural and hypothalamic thermistors. SD-32 enhanced cerebr al temperature more than SD-23 at both brain sites. The SD-induced hyp erthermia was followed by a fall of brain temperature below baseline. During recovery from either SD procedure, waking was reduced and sleep continuity increased. REM sleep was increased after SD-32. EEG slow-w ave activity (spectral power density in the 0.75-4.0 Hz band) exceeded the baseline level in the first 3-h interval of recovery; however, th e effects of SD-23 and SD-32 did not differ. In the same time interval , power density in the 1.25-1.5 Hz bin as well as in some bins in the theta and alpha band was higher after SD-32 than after SD-23. The incr ease in hypothalamic temperature during SD did not correlate with the increase in SWA during recovery. It is concluded that even a brief SD has major repercussions on recovery sleep whereas the extent of cerebr al hyperthermia during SD is only a minor factor.