The defence characteristics of the CNS barriers can be considered as both physical and biochemical barriers. The physical barrier is imparted by TJs, which are formed through a sophisticated network of interacting proteins, such as occludin, claudins, junctional adhesion molecules (JAMs) and zonula occludens, which prevent the paracellular movement of solutes (Abbott, Patabendige, Dolman, Yusof & Begley, 2010). The biochemical barrier is imparted by the function of efflux transporters, such as the ATP-binding cassette (ABC) proteins, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), that effectively exclude various endogenous and exogenous toxins from the endothelial cells. In addition to the physical and biochemical barriers, there exist a number of influx transporters, such as glucose transporter 1 (GLUT1) and large amino acid transporter (LAT1), which facilitate the uptake of essential nutrients into the CNS (Abbott, Patabendige, Dolman, Yusof & Begley, 2010). The BSCB is slightly more permeable than the BBB in mice (Pan, Banks & Kastin, 1997), likely attributed to reduced abundance of zonula occludens-1 and occludin (Ge & Pachter, 2006). Furthermore, the levels of efflux transporters and TJ proteins were reported higher in the human BBB relative to the BSCB (Uchida et al., 2020).