Longitudinal Study of Changes in Daily Activity Rhythms over the Lifespan in Individual Male and Female C57BL/6J Mice

Mice are used widely for research on circadian, molecular and other processes; however, little is known of circadian age- and, particularly, sex-related changes that occur over the entire lifespan of this species. To shed light on this question, the authors used a longitudinal design for the first continuous actogram measurements of general circadian locomotor activity rhythms unperturbed by photocycle or other experimental manipulations over the lifespan in male and female C57BL/6J mice. These weaning-to-death actograms are the most inclusive undertaken to date. Comparisons of circadian parameters (phase angle of entrainment, length of daily activity, bout length/intensity) were made among 4 life stages (adolescence, adult, middle age, and senescence). The present data reveal the progressive and sex-related changes in general locomotor activity pattern that occur throughout the lifespan. From the overall perspective of this study, there appears to be a need for wider age and sex representation in circadian research.