IL-1β and TNFα mRNA increased in old and young rats in the first 12 hours following IL-1 injection, but only old IL-1 treated rats showed a subsequent increase in protein levels of these two markers. A. Old and young rats showed a significant upregulation of IL-1β gene expression at 6 hours post-treatment compared to age-matched sham-injected rats, non-surgical controls, and IL-1 treated rats of the same age at later time points. B. In young IL-1β treated rats, TNFα mRNA is significantly upregulated at 3, 6 and 12 hr compared to non-surgical controls, and the 6 and 12 hr points compared to the 48 and 72 hr points. C. Old IL-1β treated animals upregulated IL-1β protein at 6 and 12 hr post-treatment compared to non-surgical controls as well as later time points. D. Old rats treated with IL-1β had significant elevations in TNFα protein at 6 hr compared to young IL-1β treated rats at the same time point or compared to old IL-1β treated rats at the 6 hr timepoint. A-D. n=8/group Data expressed as mean + SEM. § indicates significant difference between IL1-treated and shams within the same age and time group. # indicates significant difference between young and old within the same time and treatment group. † indicates significant difference between time groups within age and treatment group.