Fig. 1.

Astrocytes and Müller cells, the two macroglial cells of the retina, are shown in this schematic of the mammalian retina. Astrocytes are confined largely to the nerve fiber layer at the vitreal (inner) border of the retina. Müller cells, specialized radial glial cells found only in the retina, span much of the retinal depth, from the vitreal border to the photoreceptor layer. The principal neurons of the retina are illustrated, as are the recording and stimulating electrodes used in experiments to monitor glial cell modulation of neuronal spiking.