Figure 2. Cell death analysis of ON-associated apoptosis following rNAION. Optic nerve (ON) cross sections were evaluated with the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) reaction in (A) the control (naïve) animals and (B) in animals 31 days after the induction of rodent nonarteritic anterior ischemic optic neuropathy (rNAION). C: Temporal analysis of TUNEL-positive ON cells following rNAION. Retinal ganglion cell (RGC) death timing post-rNAION (taken from [5]) is superimposed. D: TUNEL analysis was greatest in the anterior ON (113.25±9.6000 standard error of the mean (SEM), n = 9) compared to the more distal portion (45.60±13.02 SEM, n=9). Asterisks indicate statistical significance (ANOVA f-ratio = 17.08519, p=0.003283). E, F: Confocal analysis of APC (oligodendrocyte marker) and a marker of apoptosis (cleaved caspase 3: C: Caspase) in longitudinal ON sections of the anterior ON (dotted line depicts the lamina). E: Control (naïve). There is minimal cleaved caspase 3 expression in the anterior ON. F: 30 days post-rNAION. There is extensive colocalization of cleaved caspase 3 and APC in the anterior ON, suggesting the oligodendrocytes are undergoing apoptosis. The ratio of cleaved caspase to APC was 6.9-fold higher in ONs 30 day post-rNAION versus naïve controls (0.36±0.05 SEM for naïve versus 2.49±0.06 SEM, n=3 ONs/group; ANOVA; f-ratio-1294.64021, p<0.00001).