AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 6 1169-R1175, Copyright © 1992 by American Physiological Society
Advance shift of feeding circadian rhythm induced by obesity progression in Zucker rats
K. Fukagawa, T. Sakata, H. Yoshimatsu, K. Fujimoto, K. Uchimura and C. Asano
First Department of Internal Medicine, School of Medicine, Oita Medical University, Japan.
To determine the relation between the circadian rhythm of ingestive
behavior and the progression of obesity in Zucker rats, ingestion and
ambulation were analyzed at four different developmental stages. The obese
rats were disrupted gradually in nocturnal patterns of feeding, drinking,
and ambulation with the progression of obesity, although the lean
littermates maintained the patterns during whole test periods. Analysis of
autocorrelogram revealed that circadian rhythms of those behaviors remained
throughout the whole test periods. Least-squares spectrum ascertained the
following. 1) The obese made advance shift of acrophases in feeding and
drinking circadian cycles, but not in ambulation. 2) Amplitudes in those
behavioral measures decreased with the progression of obesity. 3) Mesor in
the obese feeding was not affected, although that in the lean feeding
decreased. The findings indicate that disruption of the light-dark cycle in
ingestion of the obese was not due to disappearance of circadian rhythm but
to transformation by both decreased amplitude and advance shift of the
circadian cycle.
