Cytokine response. Quantitative real-time polymerase chain reaction (PCR) analyses of TNF-α (A), IL-1β (B), iNOS (C) and IL-18 (D) mRNA levels shows upregulation of all cytokines within specific time windows. A rapid strong induction of TNF-α peaking at 4 h was accompanied by a lower response of IL-1β and iNOS with a maximum at 72 h. IL-18 was induced very late around day 7. At each time point after onset of infarct, n = 5 animals were studied, whereas 4 animals served as control. Bars represent mean ± SD; **p < 0.01; *p < 0.05 (compared to control animals); ++p < 0.01; +p < 0.05 (infarcted hemisphere compared to contralateral hemisphere).