FIGURE 2.

(A) Neurovascular unit is comprised of capillary endothelium (red), mural cells such as pericytes (green) or smooth muscle cells, which share a common basement membrane (gray) with the endothelium, astrocyte foot processes (purple), which invest ∼99% of the basement membrane surface, and occasional nerve endings (blue), which directly innervate the microvascular surface. Reprinted by permission from Pardridge (2007). (B) Microvessels isolated from fresh bovine brain and stained with trypan blue. The endothelial nuclei are trypan blue positive, and the erythrocytes trapped in the lumen of the capillary are yellow. Reprinted by permission from Boado et al. (1999); copyright 1999 National Academy of Sciences. (C) Scanning electron micrograph of bovine brain microvessels show nerve endings attached to the microvessel. Reprinted by permission from Pardridge (2001).