Neuronal nitric oxide synthase is expressed in the axotomized ganglion cells of the rat retina.

This study investigated the expression and cellular localization of neuronal nitric oxide synthase in the rat retina following optic nerve transection (ONT). In the normal rat retina, nNOS immunoreactivity was localized to amacrine cells and displaced amacrine cells. A few bipolar cells were also labeled. In the axotomized retina, ganglion cells showed nNOS immunoreactivity from 3 days after ONT, and these cells increased in number, peaking 5 days after ONT. Quantitative evaluation using immunoblotting confirmed that nNOS expression showed a peak value (255% of control levels) 5 days after ONT and decreased to 137% of controls by 28 days. These findings suggest that axotomized ganglion cells degenerate via NO-mediated excitotoxicity.