Blood-Brain Barrier and Choroid Plexus

Pericytes surround brain capillaries and are integrated into the basal membrane. They exhibit contractile properties, have phagocytic activity, and release growth hormones that are necessary for the proper assembly of capillaries. 

The second barrier separating the central nervous system from blood circulation is the choroid plexus or plexus choroideus. It is formed by a vascular sponge, which is surrounded by epithelial cells (ECs) and which is located within the ventricles ofthe brain. The actual barrier is formed by the epithelial cells and not by the interior capillary. One of the major functions of the choroid plexus is the production of cerebrospinal fluid (liquor). In addition, the epithelial cells secrete ions, peptides, nutrients, and vitamins [105]. 

Subtypes of the LDL receptor can also be used for an improved drug delivery to the brain Coating of polymeric nanoparticles with surface-active compounds such as Tween 80 (polysorbate 80) leads to an association of plasma proteins such as apolipoprotein Al or apolipoprotein E with the particles and subsequently leads to an improved CNS efficiency of incorporated drugs. It has been suggested that coated particles are taken into endothelial cells via an LDL receptor [17, 125]. 

Seelig, A. (1998) A general pattern for substrate recognition by P-glycoprotein. European Journal of Biochemistry, 251, 252-261. 

and Wijnholds, F. J. (1999) The multidrug resistance protein family. Biochimica et Biophysica Acta, 1461, 347-357. 

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