AJP - Regulatory, Integrative and Comparative Physiology, Vol 234, Issue 3 130-R135, Copyright © 1978 by American Physiological Society
Comparison of synchronization of primate circadian rhythms by light and food
F. M. Sulzman, C. A. Fuller and M. C. Moore-Ede
Several circadian rhythms in squirrel monkeys (Saimiri sciureus) entrained
by two different agents were studied to compare their mode of coupling with
the environmental zeitgebers. Synchronization was accomplished either by
light-dark cycles consisting of 12 h of 600 lx followed by 12 h of less
than 1 lx (LD 12:12), or by eat-fast cycles in which the animals could eat
for 3 h and then had to fast for the remaining 21 h each day (EF 3:21). The
rhythms of drinking, colonic temperature, and urinary potassium and water
excretion were measured in chair-acclimatized monkeys. The drinking and
urinary rhythms were more reproducible (smaller mean variance) and more
stable (smaller standard deviation of the timing of a phase reference
point) in EF than in LD cycles, whereas the temperature rhythm was more
tightly controlled by LD cycles than by EF cycles. In constant light an 8-h
phase delay in the EF cycle caused the drinking and urinary rhythms to
resynchronize to the EF cycle within one day, while the temperature rhythm
required about 6 days to resynchronize. In contrast, previously published
data for a similar phase delay in the LD cycle with food available ad
libitum show that the drinking and temperature rhythms resynchronized more
rapidly than the urinary rhythms. These results indicate that separate
mechanisms are involved in transducing temporal cues from LD and EF cycles
in the circadian timekeeping system of these nonhuman primates.
