Fig. 4

Tracer introduced into the CSF penetrates into the perivascular space of arteriolar wall. For testing the potential of clearance mechanisms, we adopted the methodology used to study the ‘Glymphatic’ path, and injected Dextran (10 kDa) into the cisterna magna. a Schematic illustration of the experimental design: very small volumes of tracers are introduced into the cisterna magna and circulate in the CSF for 30 min. Cortical cross sections are used to locate fluorescent tracer signals (green circles). b Low magnification confocal microscopy of cortical sections demonstrates expected tracer signals around arteries/arterioles (arrows, CD31 + SMA double positive vessels), but not around capillaries (arrowheads, CD31 single positive vessels). Scale bar 5 µm c, Confocal microscopy imaging of an arteriole cross section demonstrates approximate co-localization of the tracer with both endothelium and smooth-muscle signals (arrows). Scale bar 10 µm (n = 3 mice, 12 arterioles)