Retinal astrocytes: their restriction to vascularized parts of the mammalian retina.

The distribution of astrocytes has been studied in whole-mounted horse and monkey retinae by the immunocytochemical localization of glial fibrillary acidic protein (GFAP). In the horse, astrocytes were found to be restricted to a narrow zone close to the optic nerve head. This is also the only region of the horse retina that is vascularized. In the monkey, astrocytes were found ubiquitously in the nerve fiber layer of the retina, apart from the avascular fovea centralis which lacked astrocytes. These observations strongly suggest that retinal astrocytes co-occur with blood vessels, a feature which may be common among mammals.