[Glia of median eminence. Electron microscopic studies of normal, adrenalectomized and castrated rats ]

The glia is investigated in an oral and middle region of the median eminence (EM). Both zones have in common that they can be subdivided in the ependyma and subependyma (with ependymal cells, tanycytes and some oligodendroglial cells, astrocytes and glia which cannot be further classified), internal zone (with astrocytes, oligodendroglia and microglia) and external zone (with astrocytic tanycytes, microglia and a few astrocytes). Quantitative differences exist between the oral and middle part of the EM since the area which is occupied by the glia decreases per section in the caudal direction. For the first time a new type of glia cells is described which are designated as astrocytic tanycyte; they posses the structural features of tanycytes as well as of astrocytes.--After adrenalectomy and castration the area of the glia is bigger in the external zone than in untreated animals. Under the same conditions the number and size of the lipoprotein granules of the glia increase. A general activation of the glia of the EM occurs which is considered to be a reaction which runs parallel with the stimulation of the neurosecretory systems.