Supraependymal cell clusters and invaginations in the epithalamic third ventricle of the rabbit (Oryctolagus...

Supraependymal cell clusters and deep invaginations of the ependymal wall, situated in the epithalamic area of the third ventricle of the rabbit have been precisely located by means of semithin serial sections. A study of these structures has been carried out using optical transmission and scanning electron microscopy. The round shaped supraependymal cell clusters revealed two types of cells: type I, of central location and bearing the morphological features of neurons and type II, located peripherically and of possible ependymary origin and nature. In the same epithalamic region, deep invaginations of the ventricular wall, lined by ependymal cells of similar morphology to those coating the rest of the third ventricle, are described. The functional role of both structures is discussed.