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.
Netherlands Institute for Brain Research, Amsterdam.
W
W
Witting
M
M
Mirmiran
N P
NP
Bos
D F
DF
Swaab
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