Body temperature and nesting behavior following influenza challenge in mice: Effects of age

We studied the interaction of age and influenza on core body temperature (T-c) of mice. Following influenza challenge, 2-mo-old female BALB/c mice demonstrated a significant fall in T-c. Female BALB/c mice 24 mo of age had lower baseline T-c than young mice and a larger fall in T-c post influenza challenge. We noted there were marked differences in nesting behavior between the young and aged mice. A nesting score was devised, and we found that at baseline, aged mice had a much lower score than young mice (15.6 +/- 7.4 vs. 24.7 +/- 0.3, P < 0.0001). Following influenza challenge, nesting behavior of young mice dropped considerably, while no significant change occurred in the behavior of aged mice. When mice were housed without bedding, there were significant decreases in T-c of young, but not aged mice. There was a further fall in T-c with influenza challenge in young mice. These data imply that ne(s)ting is an important mechanism for maintaining T-c in young mice, but alternative mechanisms are used by aged mice. The lower body temperatures in the aged mice are similar to studies in aging humans.