Functional Assessment of the Efficacy of Cop–1 Treatment for Laser–Induced Retinal Damage in the Rat

Abstract

Abstract: : Purpose: To assess the neuroprotective effect of Glatiramer acetate (Copolymer–1, Cop–1, trade name Copaxone) treatment on outer retinal function following laser–induced retinal damage in the rat. Methods:Standard argon laser lesions were created in the right eye of 16 adult, DA pigmented rats. The number of lesions was enough to cover half of the visible retina. The laser settings were found in previous studies to result in lesions of the uniform size and configuration, involving mainly the outer retinal layers. The left eye served as an untreated control. Group 1 (n=8) was treated with 200 µg Cop–1 (0.2 ml in volume emulsified with complete Freund’s adjuvant) subcutaneously, seven days prior to photocoagulation. Group 2 (n=8) was treated with saline (at the same volume) served as a control. Flash electroreinography (ERG) was performed to assess outer retinal function 3, 21 and 60 days post lasering. Ten stimuli (0.1 Hz) were recorded and averaged from each eye, and saved for further analysis. Results: Three days after laser treatment we noticed a significant decrease of ERG responses in the lasered eyes compared to the contra lateral intact eyes, though at this time there were no significant differences in ERG amplitudes between the treated an untreated animals (P>0.05). However, 21 days post–lasering we noticed a significant recovery of the ERG responses in the eyes of the treated group compared to the control group, as reflected by the ratio between lasered and intact eyes (99.7±7% and 83.5±8% respectively, p<0.05). This trend continued after 60 days, with a lasered eye:intact eye response ratio of 99.5±10% in the treated animals, and 85.8±6% in the untreated animals ( P<0.05) Conclusions: In this work we demonstrated that treatment by Cop–1 offers functional protection from argon laser retinal damage. Though outer retinal function decreased in the immediate post–laser period, it recovered 20–60 days afterwards in the treated animals. The untreated group showed a significant (P<0.05) reduction of outer retinal function in the injured eyes during this period.

Keywords: neuroprotection • retina: distal (photoreceptors, horizontal cells, bipolar cells) • laser