Brief access to sucrose engages food-entrainable rhythms in food-deprived rats.

Two studies examined whether brief access to sucrose solutions engages food-entrainable rhythms when pitted against a light-dark cycle. In Experiment 1, 32% sucrose was given once daily for 5-6 min at Zeitgeber Time 4 (ZT 4) for 17-18 days to 8 food-deprived and 8 ad-lib-fed rats. Chow was provided at ZT 16. Temperature, wheel running, activity, and corticosterone (B) anticipated sucrose only in food-deprived rats. Ad-lib rats were similar to controls. In Experiment 2, 32% sucrose was presented at ZT 4 for 5 or 10 min for 17 days to food-deprived rats. Chow was given at ZT 12. Exogenous cues were minimized. Both groups showed anticipation of sucrose, whereas room controls did not. After a shift to 4% sucrose for 8 days, the 10-min group showed signs of damping of these rhythms, whereas the 5-min group did not. Data indicated that brief access to sucrose engages food-entrainable rhythms in food-deprived rats.