Fig. 3

Large CSF tracers preferentially circulate within the spinal leptomeninges with limited entry superiorly into the spinal dura and inferiorly into the underlying parenchyma. A, B Representative wholemounts showing large CSF tracer distribution through the dorsal spinal cord dura (A) and dorsal spinal cord leptomeninges (pia and arachnoid) (B) 4 h after 15-nm gold nanoparticle (AuNP) injection into the right lateral ventricle of P7 rodents. Scalebar = 1 cm. C Representative wholemount showing 15-nm AuNP distribution through the ventral spinal cord leptomeninges 4 h after intraventricular injection into the right lateral ventricle of P7 rodents. Scalebar = 1 cm. D, Quantification of 15-nm AuNP mean intensity in the spine dura, ventral leptomeninges, and dorsal leptomeninges. There was significantly more 15-nm AuNP distribution in the leptomeninges than the dura. Data are mean ± SD, n = 3 per group; One-way ANOVA with post-hoc Tukey. E–G High magnification histology of 15-nm AuNP distribution along the leptomeninges of spinal nerve roots as they leave the spinal cord. 15-nm AuNPs distributed primarily around the roots (F), with additional diffuse 15-nm AuNPs observed inside the roots (E, G). Areas from which high-magnification images are obtained are indicated by white boxes in 2B and 2C. E–G scalebars = 25 µm. H–K Representative histology showing 15-nm AuNP distribution in the spinal cord, spinal leptomeninges and spinal dura mater. The anterior median fissure (AMF), central canal (cc), dorsal horn (DH), dorsal root (DR), dura mater (DM), arachnoid mater (AM), pia mater (PM), ventral horn (VH), subarachnoid space (SAS), root attachment zone (RAZ), and parenchyma (P) are indicated. H scalebar = 1 mm, I–K scalebars = 25 µm. All data are representative of 3 rodents