Glutamate and hypoxia as a stress model for the isolated perfused vertebrate retina.

Neuroprotection has been a strong field of investigation in ophthalmological research in the past decades and affects diseases such as glaucoma, retinal vascular occlusion, retinal detachment, and diabetic retinopathy. It was the object of this study to introduce a standardized stress model for future preclinical therapeutic testing. Bovine retinas were prepared and perfused with an oxygen saturated standard solution, and the ERG was recorded. After recording stable b-waves, hypoxia (pure N2) or glutamate stress (250 µm glutamate) was exerted for 45 min. To investigate the effects on photoreceptor function alone, 1 mM aspartate was added to obtain a-waves. ERG-recovery was monitored for 75 min. For hypoxia, a decrease in a-wave amplitude of 87.0% was noted (p<0.01) after an exposition time of 45 min (decrease of 36.5% after the end of the washout p=0.03). Additionally, an initial decrease in b-wave amplitudes of 87.23% was recorded, that reached statistical significance (p<0.01, decrease of 25.5% at the end of the washout, p=0.03). For 250 µm glutamate, an initial 7.8% reduction of a-wave amplitudes (p>0.05) followed by a reduction of 1.9% (p>0.05). A reduction of 83.7% of b-wave amplitudes (p<0.01) was noted; after a washout of 75 min the reduction was 2.3% (p=0.62). In this study, a standardized stress model is presented that may be useful to identify possible neuroprotective effects in the future.