Protection of photoreceptor apoptosis by administration of geranylgeranylacetone (GGA). TUNEL assay in the vehicle (A, D, G, J), GGA (B, E, H, K) and GGA with quercetin (C, F, I, L) 0, 1, 3 and 7 days after RD. TUNEL (+) cells were observed in the ONL. M: Quantification of transferase-mediated dUTP nick-end labeling (TUNEL) (+) cells by immunohistochemistry. Note that the number of TUNEL (+) cells was significantly lower in the GGA than in the vehicle or GGA with quercetin (*P < 0.01; **P < 0.05). N: Relative ratio of the outer nuclear layer (ONL) thickness in each group. In the all groups, the ONL thickness was decreased with time. However, decrease of the ONL thickness in the GGA group was significantly suppressed compared with another two groups of them (*P < 0.01; **P < 0.05). O: Suppression of caspase-9 activity after retinal detachment (RD) by the administration of GGA at the time point of RD in the compared with vehicle or GGA with quercetin groups (*P < 0.01; **P < 0.05). P: Suppression of caspase-3 activity after RD by the administration of GGA at the time point of RD in the compared with vehicle or GGA with quercetin groups (*P < 0.01; **P < 0.05). Each column represents the mean ± SD of six independent experiments. Scale bars = 100 um. Q, quercetin; GCL, retinal ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer.