Impermeability of newt cerebral and pial capillaries to exogenous peroxidase. A light and electron microscope study.

The permeability of cerebral vessels to exogenous peroxidase was studied in the newt. The reaction product was found only inside the cerebral or pial blood vessels. Electron microscope investigations revealed the presence of reaction product along the luminal area of vessels and in some parts of the intercellular spaces at the level of tight junctions joining endothelial cells. On the basis of the ultrastructural peroxidase localization, the presence of a brain-blood barrier in Triturus is discussed.