Possible implications of acid-sensing ion channels in ischemia-induced retinal injury in rats

Retinal ischemia in eyes with diabetic retinopathy and retinal vein occlusion leads to local tissue acidosis. Acid-sensing ion channels (ASICs) are expressed in photoreceptors and other neurons in the retina, and may play a role in acid-induced cell injury. The purpose of this study was to investigate the neuroprotective effects of amiloride, an ASIC blocker, on induced retinal ischemia in rats. Transient retinal ischemia was induced in male Long-Evans rats by the temporary ligation of the optic nerve. Just before the induction of ischemia, the experimental eyes underwent intravitreal injection of amiloride. On day 7, the retinal damage in eyes that underwent amiloride treatment (and in those that did not undergo the treatment) was evaluated by histology and electroretinogram (ERG). Transient retinal ischemia caused retinal degeneration with thinning of the inner layer of the retina. The blockage of ASICs with amiloride significantly prevented retinal degeneration. ERG demonstrated that the reduction in a- and b-wave amplitudes induced by the transient retinal ischemia was significantly prevented by the application of amiloride. The present study suggests that ASICs might, at least in part, play a pathophysiological role in ischemia-induced neurodegeneration. Blockage of ASICs may have a potential neuroprotective effect in ocular ischemic diseases.