blood-brain barrier: a standalone construct

Paul Ehrlich's 1885 dye studies first hinted at this barrier: a water-soluble dye injected into the bloodstream stained nearly every organ but left the brain and spinal cord unstained, implying that something kept the dye out of nervous tissue. Max Lewandowsky named the phenomenon the blood-brain barrier (Bluthirnschranke) in 1900, and Edwin Goldmann's 1913 experiments confirmed it by showing the reverse: the same dye injected into the cerebrospinal fluid stained the brain but not the rest of the body. The barrier is the highly selective interface, formed chiefly by the tightly sealed endothelial cells that line the brain's capillaries, that governs which molecules pass from the blood into the brain tissue, admitting oxygen, glucose, and other essentials while excluding most large or water-soluble compounds, toxins, and pathogens. Thomas Reese and Morris Karnovsky localised its anatomical basis in 1967, tracing an injected tracer protein only as far as the tight junctions between those endothelial cells, the sealed contacts that physically block passage between one cell and the next. As a landmark of neuroscience and physiology, the construct accounts for both why the brain holds a stable internal chemical environment and why delivering drugs to the central nervous system is so difficult.[1][2][3][4]

Unit

A physiological barrier defined by its location and its selective permeability at the endothelium of the brain's capillaries

Recovery means

Not applicable

Measured by

Assessed by tracer and dye permeability studies, transendothelial electrical resistance, and imaging of barrier integrity such as contrast-enhanced MRI