Time course analyses of cytokine mRNA expression indicate differences in the brain cytokine response between neonates and weanlings. Cytokine mRNA levels in brains from neonatal and weanling mice were assayed at 2, 6, 12 and 48 hpi following ic inoculation with PBS or LPS. n = 4 to 6 mice per group per time point from combined experiments. Data are presented as mean ± SEM. Statistical analysis was completed by two-way analysis of variance with Tukey’s multiple comparisons test. Significant age-specific differences in the LPS response between neonates and weanlings are indicated: **P < 0.01, ***P < 0.001.