Ion and water transport across the blood-brain barrier

This chapter presents an overview of blood-brain barrier (BBB) structure and function with an emphasis on Cl2 transporters and channels and their role in health and disease. The blood-brain barrier comprises brain microvessel endothelial cells. It is a highly specialized endothelium that provides an important anatomic and functional barrier between the blood and the brain. The BBB has unique features that set it apart from endothelial cells of other vascular beds. This includes the presence of complex tight junctions that create a barrier with very limited paracellular solute flux and a high electrical resistance between blood and brain on the order of 2000 ohm · cm2, making this barrier comparable to tight epithelia such as those found in the distal kidney and colon. The vast majority of solutes must move across the BBB via a transendothelial rather than a paracellular route and thus it is BBB transporters that determine what moves between blood and brain.