Fig. 4

Small CSF tracers primarily circulate within the leptomeninges and not the dura. A Schematic of regions shown in B–D. B–D Representative histology of decalcified skulls and the underlying meninges and parenchyma showing widespread small CSF tracer distribution within the arachnoid and pia maters over the cortex (B), inferior colliculus (C), and cerebellum (D) 10 min after 1.9-nm gold nanoparticle (AuNP) injection into the right lateral ventricle of P7 rats. There was minimal 1.9-nm AuNP (brown) distribution through the pericranium and skull, and limited tracer distribution through the dura mater along the surface of the brain. The subarachnoid space is collapsed post-mortem and differentiation between layers was primarily based on tissue morphology. scalebar = 50 µm. E Representative X-ray microtomograph (XRM) showing 1.9-nm AuNP distribution within the pia mater (PM), arachnoid mater (AM), subarachnoid space (SAS), and parenchyma (P) at the level of the inferior colliculus. Similar to observations on histology, there was minimal enhancement in the dura mater (DM) and little to no enhancement in the transverse sinus (TS, dashed white line). scalebar = 500 µm. F, G Quantification of the percent change in mean intensity increase of 1.9-nm AuNPs in the dura, arachnoid, and pia maters (F) and pia mater and parenchyma (G) compared to the background XRM signal. Data are mean ± SD, n = 3 per group; F One-way ANOVA with post-hoc Tukey. G Unpaired, two-tailed T test. All data are representative of 3 rodents