AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 1 46-R54, Copyright © 1987 by American Physiological Society
Circadian rhythms of rabbits during restrictive feeding
B. Jilge, H. Hornicke and H. Stahle
Without a zeitgeber the circadian rhythms of five physiological functions
free-ran with a period length greater than 24 h. Restricted feeding time
(RF) masked the free-running rhythms. In addition to masking, entrainment
with RF occurred. This process was most evident in locomotor activity and
visits to the food box. RF thus had zeitgeber properties in these rabbits.
However, in most rabbits the RF zeitgeber was not strong enough to entrain
the circadian rhythm completely. A small component free-ran during RF.
Following return to continuous food access the whole circadian rhythm
resumed to free-run again. In some animals its phase was determined by the
RF zeitgeber and in others by the small free-running fraction present
during RF. The results suggest that in addition to the
light-dark-entrainable circadian oscillator system a feeding-entrainable
oscillator exists that takes over phase control of the majority of the
rhythm during RF.
