Penetration barrier to sodium fluorescein and fluorescein-labelled dextrans of various molecular sizes in brain capillaries

Abstract
The permeability of the blood-brain barrier to sodium fluorescein, or fluorescein-labelled dextrans of various molecular weights, was investigated. Unlike the capillaries in both the area postrema and the eminentia mediana, the capillaries of the cerebral cortex were impermeable to all the intravenous tracer substances used.