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

Am J Physiol. 1997 Apr;272(4 Pt 2):R1219-25. doi: 10.1152/ajpregu.1997.272.4.R1219.


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.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aging / physiology*
  • Analysis of Variance
  • Animals
  • Circadian Rhythm*
  • Cricetinae
  • Darkness
  • Light
  • Male
  • Mesocricetus
  • Motor Activity*
  • Time Factors