N-Methyl-N-Nitrosourea-Induced Photoreceptor Degeneration Is Inhibited by Nicotinamide via the Blockade of Upstream Events before the Phosphorylation of Signalling Proteins

Figure 5

Retinal immunohistochemistry of pERK and GS after intraperitoneal MNU injection. Retinal cryosections from control (a), 6 hours (b, d) and 1 day (c, e) after MNU (b, c) or MNU/NAM (d, e) injection were immunostained against pERK and GS. The inner limiting membrane and the cell bodies of the inner nuclear layer were colabelled with pERK and GS antibodies 6 hours after MNU injection (arrows in (b)). One day after MNU injection, pERK immunoreactivity was observed in the outer nuclear layer and the outer limiting membrane (arrows in (c)). In addition, nuclear pERK staining was observed (arrowheads in (c)). The nuclei was stained with 4′,6-diamidino-2-phenylindole (DAPI) shown as blue. GS: glutamine synthetase; pERK: phosphorylated extracellular signal-regulated kinase; MNU: N-methyl-N-nitrosourea; and NAM: nicotinamide.