ABSTRACT

Microvascular endothelial cells of the central nervous system (CNS) substantially differ from other vascular endothelia in their capacity to strictly regulate the passage of molecules to and from the neural parenchyma. This selectivity resides in structural features unique to CNS endothelia, including expression of tight intercellular junctions that markedly limit paracellular permeability to hydrophilic molecules (Wolburg and Lippoldt 2002), a unique pattern of receptors and transporters that control the entry of nutriments into the CNS and multispecific drug export pumps that protect the CNS against a variety of hydrophobic compounds or xenobiotics (Schinkel 1999; Begley 2004). Together, these specific characters constitute the blood-brain barrier (BBB).