AGING LENGTHENS TAUDD IN C57BL 6J, DBA/2J, AND OUTBRED SWR MALE-MICE (MUS MUSCULUS)/

The effect of aging on the free-running period (TauDD) of a circadian rhythm for wheel-running activity was observed in two inbred strains ( DBA/2J and C57BL/6J) and one outbred strain (Tac: (SW)fBR) of laborato ry mice (Mus musculus). TauDD in the DBA and C57 mice was monitored at approximately age 100 days and age 300 days. TauDD in the outbred str ain was monitored at approximately age 100 days and age 600 days. TauD D increased with age in all three strains. Most studies of age effects in rodent species have shown a shortening of TauDD with age, with the exception of the C57BL inbred mice. These results show that the lengt hening of TauDD with age in laboratory mice is not limited to the C57B L strain and may be a general characteristic of this species, in contr ast to other rodent species examined.