Merck, SCC066, Blood-Brain Barrier hCMEC/D3 Cell Line

The blood–brain barrier (BBB) is a highly selective permeability barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system. The blood–brain barrier is formed by capillary endothelial cells, which are connected by tight junctions with an extremely high electrical resistivity. The blood–brain barrier allows the passage of water, some gases, and lipid soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function. On the other hand, the blood–brain barrier may prevent the entry of lipophilic, potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein. Astrocytes are necessary to create the blood–brain barrier. The blood–brain barrier (BBB) prevents entry into the brain of most drugs from the blood. The presence of the BBB makes difficult the development of new treatments of brain diseases, or new radiopharmaceuticals for neuroimaging of brain.