Behavior of adult and aged mice before and after central injection of interleukin-1 beta

The level of locomotor activity, body temperature (T-B), and feeding for ad ult (3-5-month old) and aged (22-24-month old) male BALB/c mice was determi ned and the sensitivity of the two age groups to the anorectic, febrile, an d behavioral properties of interleukin-1 beta (IL-1 beta) in the brain was examined. Baseline locomotor activity and T-B were markedly lower in aged m ice than in adults and the circadian rhythm for both activity and T-B were disrupted in the aged. Adult and aged mice consumed similar amounts of food during the daytime and nighttime, but aged mice made longer, less frequent visits to the feed cup. To determine if aging affects the responsiveness t o central IL-1 beta, adult and aged mice were injected intracerebroventricu larly with PBS or IL-1 beta. Compared to age-matched PBS controls, IL-1 bet a increased T-B in both adult and aged mice. The peak Delta T-B was greater in aged mice than in adults, but because of a lower baseline T-B in aged m ice, peak T-B after IL-1 beta was not different between groups. Locomotor a ctivity of aged mice receiving PBS was about half that of PBS-injected adul ts and was not depressed further by IL-1 beta. However, compared to age-mat ched PBS controls, centrally administered IL-1 beta depressed food intake m ore in aged mice than in adults. These data indicate that even though feedi ng, locomotor activity, and T-B are affected by aging, the central componen t of the inflammatory response mediated by IL-1 beta is retained. (C) 1999 Elsevier Science Inc.