The effect of old age on the free-running period of circadian rhythms in rat.
The free-running period is regarded to be an exclusive feature of the endogenous circadian clock. Changes during aging in the free-running period may therefore reflect age-related changes in the internal organization of this clock. However, the literature on alterations in the free-running period in aging is not unequivocal. In the present study, with various confounding factors kept to a minimum, it was found that the free-running periods for active wakefulness, body temperature, and drinking behavior were significantly shorter (by 12-17 min) in old than in young rats. In addition, it was found that the day-to-day stability of the different sleep states was reduced in old rats, whereas that of the drinking rhythm was enhanced. Transient cycles were not observed, nor were there any age-related differences in daily totals of the various sleep-wake states. The amplitudes of the circadian rhythms of active wakefulness, quiet sleep, and temperature were reduced, whereas those of paradoxical sleep and quiet wakefulness remained unchanged.
Witting
W
W
Netherlands Institute for Brain Research, Amsterdam.
Mirmiran
M
M
Bos
N P
NP
Swaab
D F
DF
D000375:Aging / Q000502:physiology*; D000818:Animals; D002940:Circadian Rhythm; D004569:Electroencephalography; D004576:Electromyography; D008027:Light; D008297:Male; D009043:Motor Activity; D051381:Rats; D011914:Rats, Inbred BN; D012890:Sleep; D014851:Wakefulness