[The development of components of the blood-brain barrier in the neocortex of the white rat].

In formation and differentiation of the hematoencephalic barrier elements in white non-inbred rats of 14 age groups (55 animals) at the ultrastructural level certain regular phases of the process have been revealed. For example, morphological maturation of endotheliocytes and pericytes occurs on the 7th day of the postnatal life. Maximal decrease in permeability of the hematoencephalic barrier takes place on the 10th day, as a consequence of liquidation of the pericapillary space between the basal membrane and the glial tunic of the capillaries. Morphofunctional maturation of the hematoencephalic barrier (the 21st day) terminates in differentiation of the pericapillary astrocytic limbs, that surround up to 85% of the capillary perimeter.