Aging and photoperiod effect entrainment and quantitative aspects
of locomotor behavior in syrian hamsters.
Scarbrough, Kathryn, Susan Losee-Olson, Edward P. Wallen and Fred W.
Turek.
Department of Neurobiology and Physiology and Center for Circadian
Biology and Medicine, Northwestern University, 2153 North Campus
Drive, Evanston, IL 60208-3520, 2Department of Biological Sciences,
University of Wisconsin at Parkside, Kenosha, WI 53141
APStracts 3:0420R, 1996.
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 weeks old) middle-aged (11-12
months) and old (15-17 months) 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, 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.
Received 15 July 1996; accepted in final form 30 October 30
October 1996.
APS Manuscript Number R401-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996