Temporal changes in cytokine RNA expression in the brain after traumatic brain injury. RNA expression of pro- and anti-inflammatory cytokines in ipsilateral brain changes in the first days to 8 weeks after injury. Initial fold changes were detected using pooled samples for each time point in a rat cytokine array. Fold changes greater than fourfold relative to baseline were subsequently verified in custom arrays by running individual samples in triplicate for each time point. Maximum fold changes were occurred for interleukin 1β (Il1β), IL-11 (Il11) and chemokine (C-X-C motif) ligand 1 (Cxcl1) at 24 hours postinjury. Maximum fold changes occurred for colony-stimulating factor 1 (Csf1) 3 to 5 days postinjury, IL-18 (Il18) peaked at 5 days postinjury and IL-1 receptor antagonist (IL-1rn) was elevated from 24 hours to 5 days postinjury. Error bars indicate standard errors of the mean. *P < 0.05.