GLIAL FIBRILLARY ACIDIC PROTEIN IN THE BRAIN OF THE CAECILIAN TYPHLONECTES NATANS (AMPHIBIA, GYMNOPHIONA) - AN IMMUNOCYTOCHEMICAL STUDY

The astroglia of adult and juvenile (metamorphosed) Typhlonectes natan s (Fischer) was investigated immunocytochemically with a monoclonal an tibody directed against glial fibrillary acidic protein (GFAP). The as troglia of this member of the Order Gymnophiona of the class Amphibia is mainly composed of radial glial cells. Their somata limit the ventr icles. They each give rise to a thick process that extends through the periventricular gray and arborizes within the neuropil. At the subpia l surface, endfeet establish the membrana gliae limitans externa. Some extraependymal radial glial cells are immunoreactive, but no mammalia n-like astrocytes are visualized. In the spinal cord, perikarya of rad ial glia are displaced from the GFAP-immunonegative ependyma. Perivasc ular endfeet and processes lining blood vessels are abundantly labeled . An increase in GFAP immunoreactivity extends from the exclusive labe ling of subpial endfeet in newborn, recently metamorphosed animals, to the subsequent staining of distal processes and of the entire cell in older juveniles. The midline glia of the brainstem is immunoreactive at all ages examined. Strong glial wedges separate and delineate fiber tracts. Radial glial fibers in the habenulae are particularly thick a nd exhibit strong GFAP immunoreactivity, even in juveniles where GFAP immunoreactivity is otherwise minimal. The pattern of GFAP immunolabel ing in the caecilian T. natans is similar to that in salamanders, but not to that in frogs.