Figure 4. Silver-intensified immunogold staining for glutamine in 6-week and 9-month-old WT and xCT KO retinas. (A–D) Representative images of glutamine immunoreactivity in the 6-week WT (A) and xCT KO (C) retinas, and 9-month WT (B) and xCT KO (D) retinas. The dark arrows in (A) and (C) indicate Müller cells, and the individual arrowheads indicate the location of the Müller cell endfeet. Scale bar = 50 µm. Insets show magnified views of the outer nuclear layer (A′–D′), inner nuclear layer (A″–D″), and GC layer (A*–D*). The cell types identified in these views include the photoreceptor cell bodies (PR), bipolar cells (BC), Müller cell bodies (MC), amacrine cells (AC), and the Müller cell endfeet (MCef). (E and F) Quantitative analysis result of glutamate in each retinal layer expressed as the percentage change in amino acid immunoreactivity for the 6-week xCT KO (C) or 9-month xCT KO (D) retinas in comparison with the age-matched WT retinas. n = 6 retinas. *p < 0.05.