Evaluating intracisternal CSF tracer influx and clearance in mouse and rat. Representative anterior (A-B) and posterior (D-E) coronal slices from mouse (A, D) and rat (B, E) brains following intracisternal infusion of Texas Red-conjugated dextran (TR-d3, MW 3kD; t = 30min post-infusion) show similar tracer distributions between species. (C, F) Un-infused rat brain slices exhibit little tissue autofluorescence. (G-J) Tissue fluorescence was evaluated in different brain regions: cortex (blue), white matter (grey), hippocampus (magenta), and subcortical structures (red) of the anterior (G-H) and posterior (I-J) brain. (H, J) Quantification of mean fluorescence intensity within each region (*P < 0.05 cortex vs. subcortical structures; ##P < 0.01 cortex vs. white matter structures; 2-way ANOVA; n = 3–4 per time point). Dashed line indicates average gray matter tissue autofluorescence level.