Diurnal rhythms of body temperature, drinking and activity over reproductive cycles.

These studies describe diurnal rhythm changes in female rats during gestation and lactation. In Experiment I, we measured the diurnal temperature rhythm (DTR) of 20 females through gestation, lactation and the post-lactational period and found that rhythm amplitude decreased during gestation and increased during lactation. Phase changes were also common features of the DTR during these states. In Experiment II, we measured drinking rhythms in 12 females during lactation and post-lactation and found phase and amplitude changes that were similar to the DTR changes seen in Experiment I. In Experiment III, we correlated the behavior of lactating females with their DTR and found that there was a consistent internal organization between behavior and Tb regardless of the degree of change in the DTR during the postpartum period. Females showing large phase changes in their DTR patterns were distinguishable from those showing smaller phase changes, however, on the basis of the absolute temporal organization of their behavior during lactation. All phase and amplitude changes disappeared immediately after pups were removed from the cage.