A new generation of model systems to study the blood brain barrier: the in vitro approach.

After an era of studying the unique permeability properties of cerebral endothelial cells with endogenous or exogenous tracers in vivo, the next generation of blood-brain barrier model systems was introduced, when the conditions for isolating the microvessels from brain tissue and culturing the endothelial cells were established. Recent advances in our knowledge of the blood-brain barrier have in part been made by studying the properties and function of cerebral endothelial cells with this in vitro approach. This review summarizes in brief the results obtained mainly from this rapidly growing field.