mRNA expression in periventricular brain tissue. mRNA expression of TNFα (A), IL-1β (B), TLR-4 (C) and HO-1 (D) in periventricular brain tissue of preterm rabbit pups with IVH (dark shaded bars; n = 6 at 24 hours and n = 6 at 72 hours) and in control pups (white bars; n = 10 at 24 hours and n = 17 at 72 hours). Expression of mRNA was determined using real-time PCR, as described in the Methods section, and levels of TNFα, IL-1β, TLR-4 and HO-1, respectively, were normalized against those of GAPDH and are given as fold change. The fold-change values were calculated by normalizing against control samples from untreated animals. Results are presented as box plots displaying medians and 25th and 75th percentiles. Differences between IVH versus control at 24 and 72 hours, respectively, were analyzed using the Mann–Whitney U test. * P <0.05, ** <0.01, *** <0.001. GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HO-1, heme oxygenase; IVH, intraventricular hemorrhage; TLR-4, Toll-like receptor-4.