Adaptation to daily meal-timing and its effect on circadian temperature rhythms in two inbred strains of mice

Inbred strains of mice differ in their adjustment to a mealtime out of phase with the light-dark cycle. When food access was restricted to the first 4 h of the light span, C3H/2Ibg mice steadily lost weight and died, while C57BL/6J mice recovered baseline levels of food intake within a few days. C57BL meal-timed mice also showed delayed circadian body temperature rhythms so that peak temperatures coincided with the time of food availability. Both strains were able to adapt when the period of food availability was gradually shifted to the first 12 h of the 16-h light period. C57BL mice again phase-delayed their body temperature rhythms, while C3H mice exhibited highly variable individual responses, and over half continued to increase temperature in anticipation of lights-off. These results suggest that the timing of body temperature rhythms of C57BL mice may be more easily altered relative to the light-dark cycle than that of C3H mice.This work was supported in part by NIH Grant GM 21993 to C.B.L.