AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 1 22-R29, Copyright © 1993 by American Physiological Society
Circadian properties of anticipatory activity to restricted water access in suprachiasmatic-ablated hamsters
R. E. Mistlberger
Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada.
This study provides evidence that anticipation of daily water access in
hamsters is regulated by nonphotically entrainable circadian oscillators
located outside of the suprachiasmatic nuclei (SCN). Intact and SCN-ablated
hamsters receiving 2 h/day water access ate large meals (representing
17-55% of daily food intake) during the 2-h access time. Two of nine
SCN-intact hamsters, five of five hamsters with partial SCN ablations, and
seven of nine hamsters with total SCN ablations showed anticipatory
wheel-running rhythms synchronized to water access time. These anticipation
rhythms usually disappeared during subsequent ad libitum water access but
reappeared when the hamsters were water deprived for 2 days. When the water
restriction schedule was shortened to an 18-h interval in six SCN-ablated
hamsters, an 18-h activity rhythm emerged that usually did not persist
during water deprivation. When the schedule was lengthened to 30-h
intervals, several hamsters showed 27- to 29-h rhythms that did not stably
synchronize to water access time. These results indicate that hamsters,
like rats, possess a non-SCN-based water- and/or food-entrainable,
self-sustaining oscillator with circadian limits to entrainment.
