LPS/HI triggers rapid inflammatory responses in neonatal mouse brains. (a) RT-qPCR analysis suggested elevated expression of multiple pro-inflammatory and neutrophil/monocyte-recruiting cytokines in the ipsilateral (R) hemisphere at 6 h after HI or LPS/HI injury compared with unchallenged (UN), LPS-injected, or the contralateral (L) hemisphere, although the cytokine induction patterns by HI-versus-LPS/HI were not identical. Of note, LPS/HI injury is far more potent for inducing the Csf3 mRNA. (b, c) Detection of leukocyte infiltration in LPS/HI-injured murine brains by flow cytometry. Representative flow plots (b) and quantification (c) showed increase of CD45hiCD11b+ leukocytes, CD45hiCD11b+Ly6G+ neutrophils, and MHC class II+ myeloid cells in the brain from 6 to 48 h after LPS/HI injury. Each dot on bar graphs represents an individual animal. Data were shown as mean ± SD. *p < 0.05, **p < 0.01, ***p < 0.001, by one-way ANOVA followed post hoc analysis of Tukey test and unpaired Student’s t test in panels a and c, respectively.