Phosphorylation of GluR1. A. Phosphorylation of GluR1 at Ser-831 increased at 6 hrs after optic nerve crush. B. GluR1 protein levels remained relatively constant, while phosphorylation of Ser-845 increased by 6 hrs. C-F. Immunohistochemistry of phosphorylated GluR1 (Ser-845) at 0, 0.5, 1, and 6 hrs after optic nerve crush. Increased pGluR1 is apparent in the ganglion cell layer (arrowheads) at 6 hrs after optic nerve injury. Red, = pGluR1, Blue = DAPI. IS, inner segment; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer.