Aging alters feedback effects of the activity-rest cycle on the circadian clock

O. Van Reeth*, Y. Zhang, P. C. Zee, F. W. Turek

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Two different stimuli (i.e., benzodiazepines and dark pulses) inducing phase shifts in the circadian clock of young hamsters through changes in the level of activity do not induce phase shifts in old hamsters, despite the fact that these stimuli induce a similar acute change in locomotor activity in young and old animals. In contrast, old hamsters remain sensitive to the phase-shifting effects of stimuli clearly not associated with any change in locomotor activity (i.e., protein synthesis inhibitors or light). Thus the circadian system of old animals becomes selectively unresponsive to synchronizing signals mediated by the activity-rest state of the animals. Previous age-related changes in circadian rhythmicity that have been observed in mammals, including humans, may be related to a weakened coupling between the activity-rest cycle and the circadian clock.

Original languageEnglish (US)
Pages (from-to)R981-R986
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number4 32-4
StatePublished - 1992


  • benzodiazepines
  • dark pulses
  • phase shifts

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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