Immunocytochemical demonstration of astrocytes in the eighth cranial nerve of the red-eared turtle.

Coronal sections through the eighth cranial nerve and medulla of the red-eared turtle were immunocytochemically stained for the astrocytic intermediate filament protein, glial fibrillary acidic protein. Reaction product appeared in the medial one-third of the eighth cranial nerve fibers as they penetrated the medulla. The remaining two-thirds of the nerve did not show any staining for glial fibrillary acidic protein. The lateral aspect of the nerve corresponds with the extracranial portion of the nerve. When the eighth cranial nerve of the turtle has been transected extracranially it still regenerates into the cochlear nuclei. Results of the present study indicate that the eighth cranial nerve was transected in earlier studies in a region devoid of astrocytes.