Fig. 2.

Effects of intracerebral injection of increasing doses of IL-1β on blood–brain barrier permeability, recruitment of neutrophils and expression of IL-1β and ICAM-1 at P14. At 4 h an inverse relationship was found to be present between the intracerebral dose of IL-1β and subsequent neutrophil recruitment and blood–brain barrier breakdown at P14 (A–C). (A) Representative spatial maps of neutrophil distribution in the brain and micrographs of tissue stained for neutrophils (brown; anti-neutrophil serum) and vessels (pink; laminin), showing extensive neutrophil recruitment with 1 ng IL-1β, which reduced as the dose of IL-1β was increased. (B) Immunohistochemistry for IgG shows entry of the endogenous protein into the brain tissue after the intracerebral injection of IL-1β at all doses, with the most staining observed following the 1 ng dose of IL-1β. (C) Neutrophils were found in significantly larger numbers in both the vessel lumen and brain parenchyma in the 1 ng IL-1β group compared to higher doses. (D) IL-1β and ICAM-1 mRNA expression levels were measured in the contralateral striatum of naïve mice and ipsilateral striatum of mice that received intracerebral injection of saline or 1 ng, 10 ng or 100 ng IL-1β at P14. Data are represented as relative fold change from contralateral expression in naïve mice, and show a dose dependent increase in brain gene expression with intracerebral IL-1β injection. Scale bar = 50 µm. ^*p < .05 and p < .001. ^##p < .01 vs. all parenchyma values in C. n = 3 for immunohistochemistry analysis; n = 4 for RT-qPCR. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)