Immunofluorescent localization of GFAP by confocal microscopy. Nuclei in the GCL, INL, and ONL were counterstained with DAPI. (a) GFAP expression was restricted to the end feet of Müller cells (arrow) in a control retina (10 mm Hg). (b) The retina incubated at 25 mm Hg showed positive fluorescence only in the end feet of the Müller cells (arrow). (c) A retina incubated at 50 mm Hg showed positive fluorescence (arrowheads) throughout the Müller cell body along with the end feet of Müller cells (arrow). (d) At 75 mm Hg, prominent GFAP expression was observed throughout the Müller cell body (arrowheads) along with the end feet of the Müller cells (arrow). (e) After administration of 1.0 mM glutamate, GFAP expression was restricted to the vicinity of the Müller cell end feet (arrowheads). (f) Müller cells expressed prominent immunolabeling for GFAP throughout the length of the cell body (arrowheads) along with the end feet of the Müller cells after a combination of pressure loading (75 mm Hg) and 1.0 mM glutamate. Scale bar, 20 μm.