The effects of short periods of immobilization on the hamster circadian clock

O. Van Reeth*, D. Hinch, J. M. Tecco, Fred W Turek

*Corresponding author for this work

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

Recent findings indicate that stimuli which induce an acute increase in locomotor activity can induce phase shifts in the circadian clock of hamsters. Support for the actual role of the acute increase in activity in the mediation of these phase shifts is provided by the observation that immobilization can totally block phase shifts in the activity rhythm that are normally induced in response to exposure to two of these stimuli, either a pulse of darkness or an injection of a benzodiazepine. In order to further examine the effects of immobilization on the circadian system of hamsters, 3 studies were carried out. In a first study, the effects of a 3-h period of immobilization procedure on the phase of the free running circadian rhythm of locomotor activity were tested at 8 different circadian times. Immobilization during the highly active part of the animal's activity cycle resulted in phase delays in the activity rhythm, while immobilization at other circadian times had little or no effect on the circadian time-keeping system. In two other studies, we reported that immobilization had no effect on phase shifts normally induced by 3-h pulses of light or injections of the protein synthesis inhibitor, cycloheximide, two stimuli that are clearly not associated with an increase in locomotor activity in hamsters. Thus, the ability of immobilization to block stimulus-induced phase shifts in the circadian clock appears to be specific to those stimuli that induce an acute increase in locomotor activity. Taken together with previous findings, these results indicate that stimulation of activity during the normal rest period, or prevention of activity during the normal active period, can induce phase shifts in the circadian clock, and support the hypothesis that feed-back signals during both the rest and active phases of the circadian rhythm of locomotor activity can influence the circadian pacemaker underlying this rhythm.

Original languageEnglish (US)
Pages (from-to)208-214
Number of pages7
JournalBrain Research
Volume545
Issue number1-2
DOIs
StatePublished - Apr 5 1991

Keywords

  • Activity
  • Circadian
  • Clock
  • Cycloheximide
  • Immobilization
  • Light
  • Rhythm

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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