Fig. 4

Kinetics of fluorescent tracers of differing molecular weights in the perivascular spaces of penetrating and pial arteries in the Hspg2^+/+ and Hspg2^∆3∆91 mice. A) Schematic setup with the location of the cranial window (circle) and the timeline of the imaging experiment. B) Image of cortical blood vessels (red, i.v. rhodamine). B) with the locations (1 and 2) of the bleaching experiment. C) Series of images showing baseline, bleach and recovery of the tracer (green), when injected via the cisterna magna, around the pial and in the penetrating vessels. D-E) Plots indicating a faster recovery of fluorescence post bleaching next to the pial artery and less steep recovery around the penetrating artery. F) Analysis of the half-time of recovery, showing no significant difference between tracers of different molecular weights (FITC-40 kDa and FITC-2000 kDa) around the pial vessels in the Hspg2^+/+ (n = 6–7) and Hspg2^∆3∆91(n = 6–7) mice. G) Analysis demonstrating a significant increase in the half-time of the recovery of FITC-2000 kDa tracer as compared to FITC-40 kDa around the penetrating arteries in the Hspg2^+/+ (n = 6–7) mice but not in Hspg2^∆3∆91(n = 6–8). Scale bar, 50 μm (B, C). The statistical test used was the multiple unpaired two-tailed t-test with Welch’s correction followed by Benjamini and Hochberg correction for multiple t-tests (F, G). **p < 0.01. ns, non-significant. Mean ± SEM