Reversibility of glutamate-mediated Müller cell swelling. (a) Glutamate (1.0 mM) administered at normal pressure for 30 minutes induced swelling of the Müller cell end feet (*) in the GC layer and in the nuclei (arrows). Black arrowheads and arrows: swelling of Müller cell bodies and nuclei, respectively. There was swelling of Müller cell bodies in the outer nuclear layer (white arrowheads). OLM, outer limiting membrane. (b) Müller cell swelling induced by 1.0 mM glutamate was not present 20 hours after removal of glutamate from the medium. OLM, outer limiting membrane. (c) The reversal of Müller cell swelling during incubation in glutamate-free medium was prevented by elevated pressure (75 mm Hg) for 20 hours. (*) Swelling of the Müller cell end feet. There was swelling of Müller cell bodies in the IPL, INL, and ONL. Arrowheads: the degenerated or pyknotic GC nuclei. OLM, outer limiting membrane. (d) Incubation with 1.0 mM glutamate after pressure loading (75 mm Hg) for 20 hours induced apparent swelling of the Müller cell end feet (*) in the GCL. Black arrowheads and arrows: the swelling of the Müller cell bodies and nuclei, respectively. There was a remarkable swelling of the Müller cell bodies in the ONL (*). Arrowheads: degenerated or pyknotic GC nuclei. OLM, outer limiting membrane. Scale bar, 15 μm.