Fig. 1From: In vitro modeling of the neurovascular unit: advances in the fieldSchematic view of a typical brain microcapillary. Note that the passage of substances across the BBB endothelium is controlled by a multimodal barrier system; (1) gating barrier (tight junctions) which prevents paracellular diffusion of polar molecules. Note that the adherens junction play the critical role of keeping the cell membrane of adjacent endothelial cells close together, thus allowing for the formation of the tight junctional bindings; (2) transport barrier which includes number of active efflux systems (P-gp, MRPs, etc.) with affinity for lipophilic substances; (3) metabolic/enzymatic barrier (cytochrome P450 enzymes, MAO, etc.) which catalyze the oxidation/metabolism of organic substrates including xenobiotic substances such as drugs and other potentially toxic chemicalsBack to article page