AGING LENGTHENS CIRCADIAN PERIOD FOR WHEEL-RUNNING ACTIVITY IN C57BL MICE

Previous reports of age effects on circadian period in rodents show a slight shortening of period with age, with the exception of house mice (Mus domesticus) where a number of studies report mixed results. The present study consists of three comparisons of circadian period for wh eel-running activity in young vs. older C57BL inbred mice following en trainment to 16:8 LD, 12:12 LD and 8:16 LD photoperiods. The free-runn ing circadian period (tau(DD)) for wheel-running activity was signific antly longer in older mice following entrainment to all three photoper iods. These results support a model of heterogeneous effects of aging on circadian period among different rodent species, and suggest that t he lengthening of circadian period with age in house mice is not a fun ction of age-dependent differences in after-effects imposed by prior e ntrainment.