AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 3 320-R330, Copyright © 1985 by American Physiological Society
Circadian rhythms of sleep and wakefulness in mice: analysis using long-term automated recording of sleep
G. S. Richardson, M. C. Moore-Ede, C. A. Czeisler and W. C. Dement
Circadian rhythms of wheel-running activity and polygraphically defined
wakefulness, rapid-eye-movement (REM) sleep and non-REM (NREM) sleep were
continuously observed in ten mice (Mus musculus) under both alternating
light-dark (LD 12:12) and continuous darkness (DD) conditions. Sleep-wake
state was determined automatically using a computer-based method that
allowed continuous recordings of from 60 to 280 days in duration. The
sleep-wake state percentages (of the circadian cycle) thus obtained were in
substantial agreement with other estimates for this or similar strains and
showed no significant difference between LD 12:12 (wake 54.3%, NREM sleep
38.1%, REM sleep 7.6%) and DD (wake 53.1%, NREM sleep 39.9%, REM sleep
7.0%) conditions. All 10 mice exhibited clear circadian rhythms in each of
the three states and wheel-running activity under both lighting conditions
for the entire duration of observation. Probability functions, computed
using stationary sections of data from all 10 mice, showed distinct
waveforms for all three states and wheel running. These waveforms were
remarkably similar under entrained and free-running conditions. This
documentation of sustained circadian rhythmicity in sleep-wake state
throughout observations of unprecedented length contradicts the currently
common assertion that circadian control of sleep state is weaker than that
of activity.
