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Circadian rhythms and sleep have additive effects on respiration in the rat
Author(s) -
Stephenson Richard,
Liao Kiong Sen,
Hamrahi Hedieh,
Horner Richard L.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00225.x
Subject(s) - non rapid eye movement sleep , circadian rhythm , wakefulness , free running sleep , sleep (system call) , slow wave sleep , dark therapy , psychology , k complex , sleep onset , sleep and breathing , electroencephalography , medicine , anesthesia , endocrinology , neuroscience , breathing , light effects on circadian rhythm , circadian clock , insomnia , psychiatry , computer science , operating system
1 We tested two hypotheses: that respiration and metabolism are subject to circadian modulation in wakefulness, non‐rapid‐eye‐movement (NREM) sleep and rapid‐eye‐movement (REM) sleep; and that the effects of sleep on breathing vary as a function of time of day. 2 Electroencephalogram (EEG), neck electromyogram (EMG) and abdominal body temperature ( T b ) were measured by telemetry in six male Sprague‐Dawley rats. The EEG and EMG were used to identify sleep‐wake states. Ventilation ( V̇ I ) and metabolic rate ( V̇ CO2 ) were measured by plethysmography. Recordings were made over 24 h (12:12 h light:dark) when rats were in established states of wakefulness, NREM sleep and REM sleep. 3 Statistically significant circadian rhythms were observed in V̇ I and V̇ CO2 in each of the wakefulness, NREM sleep and REM sleep states. Amplitudes and phases of the circadian rhythms were similar across sleep‐wake states. 4 The circadian rhythm in V̇ I was mediated by a circadian rhythm in respiratory frequency ( f R ). Tidal volume ( V T ) was unaffected by time of day in all three sleep‐wake states. 5 The 24 h mean V̇ I was significantly greater during wakefulness (363.5 ± 18.5 ml min −1 ) than during NREM sleep (284.8 ± 11.1 ml min −1 ) and REM sleep (276.1 ± 13.9 ml min −1 ). V̇ CO2 and V T each significantly decreased from wakefulness to NREM sleep to REM sleep. f R was significantly lower in NREM sleep than in wakefulness and REM sleep. 6 These data confirm that ventilation and metabolism exhibit circadian rhythms during wakefulness, and NREM and REM sleep, and refute the hypothesis that state‐related effects on breathing vary as a function of time of day. We conclude that the effects of circadian rhythms and sleep‐wake state on respiration and metabolic rate are additive in the rat.