The shape and distribution of astrocytes in the retina of the adult rabbit.

Astrocytes stained by antibodies to glial fibrillary acidic protein (GFAP) were examined in whole-mount preparations of retinae from adult rabbits and found to be restricted to the medullary rays. Astroglial cells exhibited a variety of shapes that varied between two extreme morphologies. One extreme was an astrocyte that possessed a few sturdy primary processes as well as finer processes and was strongly GFAP positive. The other extreme was an astroglial cell that displayed a star-shaped appearance; its perikarya gave rise to a few thin, radially oriented processes, which were rather weakly GFAP positive. The majority of astroglial processes were aligned with the ganglion-cell axons, but some of their processes were in contact with capillaries. It has been proposed that astrocytes are specifically associated with ganglion-cell axons. Their restriction to the medullary rays in the retina of the rabbit suggests, however, that their physiological role is also concerned with the vascular system.