Cytochemical localization of alkaline phosphatase in the ependyma of the rat medulla oblongata.

The ependyma of the IVth ventricle and the central canal of the rat medulla oblongata was investigated using the cytochemical technique for alkaline phosphatase (A1Pase) which revealed two types of ependymal cells in the medulla. The central canal type of the ependymal cell occupying the dorsal part of the central canal in the lower medulla exhibited intense A1Pase activity with light microscopy. These cells had reaction products in all plasma membranes, including the microvilli and the cilia at the luminal cell surface. Some cells appeared to be tanycytes, since the process reached the basement membrane of the parenchymal blood vessel. The ventricular type of ependymal cells, which form the floor of the IVth ventricle and the central canal, contained no reaction products in any structure of the luminal cell surface. The possible relationship between the cerebrospinal fluid and the nervous tissues through the ependymal linings is discussed.