THE ACTIVITY OF THE FEMALE ALBINO RAT DURING LACTATION

Abstract

An apparatus is described for recording electrically the spontaneous activity of rats during the course of lactation. Using this apparatus, the pattern of activity has been measured in lactating rats living in natural lighting (controls) and in the dark (experimental animals). All rats spent more time on their nests by day than by night but this difference was less marked in the animals living in the dark. The length of time spent on the nest during 24-hr. periods decreased with the progress of lactation in both groups of animals, and the rate of decrease was the same in both groups of animals. All animals were active for a longer period by night than by day, but the difference between the night and day activity was significantly less in the experimental animals than in the controls. Night activity was characterized by a significantly greater number of bursts separated by shorter quiescent intervals. This pattern of activity was not modified by confinement in the dark. The total duration of spontaneous activity within each 24-hr. period increased significantly as lactation progressed. This was accompanied by a significant increase in the number of bursts of activity and a corresponding decrease in the mean duration of the interval between these bursts. Confinement in darkness was without significant effect on these changes. These findings are discussed in relation to the impairment of lactation which takes place when the doe is deprived of the visual stimulus. It is concluded that this impairment is unlikely to be due to any change in the maternal behaviour of the doe.