β-Catenin and Adherens Junctions in Tanycytes and Ependymocytes of the Third Ventricle Floor of Rat Brain in Postnatal Development

β-catenin is one of the main proteins of adherens intercellular junctions, which are important for maintaining tissue integrity and the formation of apical-basal cell polarization. In the brain, adherens junctions are also important for maintaining the physiological integrity of the barriers formed by the ventricular lining cells. The purpose of this study was to analyse the distribution of β-catenin in ependymocytes and tanycytes of the third ventricle of the rat brain during postnatal development. It was found that the distribution pattern of adherens junctions in the lining cells of the third ventricle differs in the areas occupied by ependymocytes and tanycytes, as well as changing during postnatal development. In ependymocytes, this type of cell contact performs a mechanical function, participating in the formation of a continuous ependymal layer, and is also important for maintaining its integrity in early postnatal development and during aging, which is characterized by an increase in the size of the ventricles. In tanycytes, in addition to the formation of intercellular contacts, adherens junctions are important for the formation of bundles of processes and their stabilization. Thus, β-catenin, as part of adherens junctions in the lining of the third ventricle, performs several functions, including a mechanical function, uniting cells into a single layer, and is important for the stabilization of processes.