G. Casadesus et al., Automated measurement of age-related changes in the locomotor response to environmental novelty and home-cage activity, MECH AGE D, 122(15), 2001, pp. 1887-1897
The likelihood to explore in an open-field environment decreases with age.
Older animals tend to be less active and explore less both in novel and hom
e-cage environments. The locomotor performance (fine movements, ambulatory
movements, and rearing) of male Fischer 344 (17344) rats that were 6 (n=6)
or 22 (n=6) months of age was evaluated by continuous automated counting of
photobeam interruptions, every 30 min, during 60 consecutive hours, in sta
ndard polycarbonate cages. Novel environment performance was determined by
photobeam interruption counting during the first hour in the new cage. The
remaining 59 h were evaluated as home-cage activity. A significant age-rela
ted decrease in ambulatory and fine motor activity was seen during the firs
t hour of testing (novel environment). In addition, aged rats showed a decr
eased number of ambulatory and fine movements in home-cage activity, predom
inately during the dark portion of the light cycle and during or around bot
h light-switch periods (05:00 and 17:00). No differences were seen in reari
ng behavior. These findings provide a more detailed analysis and additional
evidence of the activity decreases and rhythmic changes seen in aged F344
rats under uninterrupted testing conditions. Published by Elsevier Science
Ireland Ltd.