Rb. Mcdonald et al., Alterations in endogenous circadian rhythm of core temperature in senescent Fischer 344 rats, AM J P-REG, 45(3), 1999, pp. R824-R830
Citations number
27
Categorie Soggetti
Physiology
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
We assessed whether alterations in endogenous circadian rhythm of core temp
erature (CRT) in aging rats are associated with chronological time or with
a biological marker of senescence, i.e., spontaneous rapid body weight loss
. CRT was measured in male Fischer 344 (F344) rats beginning at age 689 day
s and then continuously until death. Young rats were also monitored. The ra
ts were housed under constant dim red light at 24-26 degrees C, and core te
mperature was recorded every 10 min via biotelemetry. The CRT amplitude of
the body weight-stable (presenescent) old rats was significantly less than
that of young rats at all analysis periods. At the onset of spontaneous rap
id weight loss (senescence), all measures of endogenous CRT differed signif
icantly from those in the presenescent period. The suprachiasmatic nucleus
(a circadian pacemaker) of the senescent rats maintained its light responsi
veness as determined by an increase in c-fos expression after a brief light
exposure. These data demonstrate that some characteristics of the CRT are
altered slowly with chronological aging, whereas others occur rapidly with
the onset of senescence.