Figure 4. Effect of diabetes on the protein levels of NMDA receptor subunits. Total retinal extracts were prepared from rat retinas with one, four, and 12 weeks of diabetes (black bars) and from age-matched control rats (white bars). Extracts were assayed for (A) NR1, (B) NR2C, and (C) NR3A subunits immunoreactivity by western blot analysis. Representative western blots are presented above the graphs for each time point tested. The densitometry of each band was analyzed. The results are expressed as percentage of age-matched controls and are presented as the mean±SEM, for the indicated number of animals. In each western blot analysis, a reprobing for detection of α-tubulin was performed to confirm that similar amounts of protein were applied to the gel. The asterisk indicates a p<0.05, the double asterisk indicates a p<0.01, and the triple asterisk indicates a p<0.001, significantly different from control, using the two-tailed Student’s t-test.