Aqueductal tanycytes in the rabbit brain: A Golgi study.

Utilizing Golgi-Cox impregnation, tanycytes were found in the ependyma of the cerebral aqueduct of the neonatal and adult rabbit. These tanycyte somas showed a variety of shapes, apical projections into the aqueduct, and basal processes (shafts) projecting into the mesencephalon, particularly into the periaqueductal gray (PAG). The shafts showed a variety of branching patterns, and sometimes abutted or terminated on capillaries or on specific neuronal elements. Other shafts coiled within the PAG or terminated within the neuropil of the mesencephalon. It is possible that these tanycytes provide a route for transport of cerebrospinal-fluid-borne substances from the aqueduct to the neuronal regions and vasculature of the mesencephalon. The presence of these tanycytes with complex branching patterns in proximity to neural and vascular structures suggests a permanent, active role for these specialized ependymal cells.