Routes of fluorescent dextran entry into the brain from CSF. (A) Left: Distribution of 70-kD dextran in brain after low- and high-volume cisternal injections. Center and right: Fluorescence images of the boxed regions at the left, showing the distribution of 2,000-kD FITC dextran, 70-kD TRITC dextran, and 10-kD Alexa Fluor 647 dextran in brain perivascular space and parenchyma. (B) Left: Depth of dye penetration into the perivascular spaces of cortex (n = 6 mice, *1, P = 0.0074; *2, P = 0.0165; *3, P = 0.0188, repeated-measures two-way ANOVA with Bonferroni posttest). Differences with dextran size not significant. Right: Depth of dye penetration into parenchyma (*1, P = 0.0451; n.s.2, P > 0.999; n.s.3, P > 0.999, repeated-measures two-way ANOVA with Bonferroni posttest). (C) Routes of solute uptake of cisternally injected 70-kD TRITC dextran, counterstained with CD31 (labels all vessels) and α-SMA (labels arterioles). a, descending arteriole; v, ascending venule.
