2.1 BBB and BSCB physiology
The CNS barriers are formed by a layer of endothelial cells separating the blood and the CNS parenchyma (Figure 1 ), with the BBB and BSCB protecting the brain and spinal cord, respectively, from blood-derived toxins. The endothelial cells are connected by inter-endothelial TJ and adhesion proteins. A basement membrane supports the brain or spinal cord endothelial cell and associated pericytes, with astrocytic end-feet ensheathing the basement membrane (Abbott, Patabendige, Dolman, Yusof & Begley, 2010) (Figure 1 ).