Aging and photoperiod affect entrainment and quantitative aspects of locomotor behavior in Syrian hamsters

Kathryn Scarbrough*, Susan Losee-Olson, Edward P. Wallen, Fred W. Turek

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Aging affects the regulation of diurnal and circadian rhythmicity. We tested the hypothesis that the age-related difference in the phase angle of entrainment of the locomotor activity rhythm to a light-dark (LD) cycle would be greater under LD 6:18 than LD 14:10. We also analyzed changes in quantitative aspects of wheel-running behavior according to age group. Young (9-wk-old), middle-aged (11- to 12-mo-old), and old (15-to 17-mo-old) male golden hamsters were entrained to a 14:10 LD cycle followed by re-entrainment to a 6:18 LD cycle. Fourteen days after the start of locomotor recording in LD 14:10 and again after 27 days in LD 6:18, the phase of activity onset, the total number of wheel revolutions performed per day, the peak intensity of wheel-running activity, the duration of the active period, and the level of fragmentation of locomotor activity were quantitated. We also studied the temporal distribution of the largest bout of wheel-running activity among the age groups in both photoperiods. Short days induced testicular regression at a similar rate among young, middle-aged, and old hamsters. The data are discussed in terms of the effects of age on overall circadian organization in the seasonally changing environment.

Original languageEnglish (US)
Pages (from-to)R1219-R1225
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number4 41-4
StatePublished - May 24 1997


  • amplitude
  • day length
  • diurnal
  • phase
  • seasonal

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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