The glial architecture of the median eminence of the Mongolian gerbil (Meriones unguiculatus); a study of glial fibrillary acidic protein (GFAP) immunoreactivity in semithin sections.

The glial architecture of the median eminence (ME) of the Mongolian gerbil (Meriones unguiculatus) was studied immunohistochemically. For this purpose, semithin sections of the proximal ME were processed according to the PAP technique using antibodies directed against glial fibrillary acidic protein (GFAP). Various glial cells were stained. Their distribution, the arrangement and morphology of their processes, and the spatial relations with adjacent tissue components could be examined in detail. Most of the immunoreactive cells were identified as either tanycytes (present throughout the internal zone, but preferentially located in the ependymal and subependymal layer), or as tanycyte-like cells (present throughout the external zone, but preferentially situated in the reticular layer). The processes of both cell types established numerous contacts with capillaries of the primary portal plexus in the external zone. Moreover, many projections of tanycyte processes to capillaries of the internal zone were revealed, most notably in the subependymal layer. Peculiar uni- and bipolar cells could be detected in the fibre layer of the internal zone, the processes of which were oriented parallel to the course of the axons of the hypothalamo-neurohypophyseal system. It was demonstrated that the methodology used to study the glial cells of the ME was also well applicable to the neural lobe. This technique, therefore, provides a valuable tool for the precise visualization of the majority of glial cells in the whole neurohypophysis of the gerbil. Thus, by sequential immunostaining of serial semithin sections investigations concerning the presence of multiple substances within single neurohypophyseal glial cells become possible.