[Ultrastructural signs of the absorption of substances by the ependyma of the III ventricle in rats in the perinatal period].

The distribution of pinocytic vesicles, relief of apical surface and intercellular contacts were studied by means of electron microscope in ependyma of ventral region of III ventricle during perinatal period in rats. Morphological evidence was obtained for the fact that substances are absorbed by ependyma via pinocytic vesicles from the liquor beginning at least from the 16th day of prenatal development. During the postnatal period the intensity of absorption in the ventrolateral region of infundibulum of III ventricle and along the periphery of its extended part is higher than in the ventral region. At the same time the number of evaginations of the apical surface increases, especially in the ventrolateral region of infundibulum and along the periphery of its extended part. As a result, numerous depressions are formed on the ependyma surface, thus creating favourable conditions for the absorption of substances, circulating in the liquor. Changes in the apical surface configuration is provided by a special system of filaments. The apical parts of cells during perinatal period are girdled by a zone of specialized contacts, including cleft contacts, zones of adhesion and zones of closure. The latter, as known, limit markedly the penetration of substances.