A-1 BLLOD-BRAIN BARRIER: A GATEWAY TO NEUROLOGICAL DISEASES

other aniline dyes did not stain the brain and spinal cord of rabbits after intravenous administration [1]. Later on his disciple Edwin Goldmann in 1912 further added to this that administration of Evans blue into the ventricular system stained deeply the brain tissue, however, the dye could not be seen into the blood stream. These fundamental discoveries in Berlin, Germany about 100 years ago has given two important concepts of the barrier system, namely the blood-brain barrier (BBB) and brain-blood barrier [1-3]. However, very little is known till today about the functional implication of these barriers in health and disease. Lina Stern proposed the concept of the “blood-brain barrier ” in 1921 [3]. At that time it was believed that astrocytes rather than endothelial cells are the seat of the blood-brain barrier because of the densely packed astrocyte processes that surround the epithelial cells of the BBB [2.3]. However, the role of endothelial cells in maintaining the barrier functions was only established in 1960s when the scanning electron microscope was available [2]. Transmission electron microscopy demonstrated presence of tight junctions between cerebral endothelium that comprise the physical part of the BBB [1,2]. The barrier between blood and cerebrospinal fluid (CSF) was discovered by Hugh Davson in 1959. Electron microscopic studies further show that the endothelial cells of the choroid plexus are fenestrated and do not constitute the barrier. On the other hand, the tight junctions are located between apical sides of the choroid epithelium constituting the anatomical seat of the blood-CSF barrier (BCSFB). However, th