The Permeability of Brain Capillaries to Non‐Electrolytes

Crone, C. The permeability of brain capillaries to non‐electrolytes . Acta physiol. scand. 1965. 64 . 407–417. – By means of the“Indicator diffusion” method blood‐brain barrier permeability characteristics were studied on dogs. The permeability coefficient of fructose, glycerol, propylene glycol, urea, thiourea, antipyrine, ethanol, propanol and butanol was calculated. If these substances are ordered according to their rate of passage from blood into brain tissue a hierarchy is found which corresponds to that which is typical of the permeability of cell membranes to non‐electrolytes. The experiments lend support to the view advanced by the late August Krogh that the permeability characteristics of the blood‐brain barrier are analogous to those of cell membranes in general. This conclusion is discussed against the background of recent findings of morphologically‐demonstrated tightness of cerebral capillaries which imply that material which diffuses from blood into brain tissue must pass the plasma membranes of the endothelial cells.