MK-801 HAS NEUROPROTECTIVE AND ANTIPROLIFERATIVE EFFECTS IN RETINAL LASER INJURY

Purpose. Treatment of the retina by laser photocoagulation often is co mplicated by an immediate side effect of visual impairment, caused by unavoidable, laser-induced destruction of healthy tissue adjacent to t he lesion. A neuroprotective therapy that salvages this healthy tissue might enhance the benefit obtained from the treatment This study was proposed to determine whether glutamate-receptor blockers can provide adjuvant neuroprotection during laser photocoagulation. The effect of MK-801, an NMDA-receptor antagonist, on laser-induced retinal injury w as examined, in a rat model. Methods. Argon laser lesions were created in the retinas of 36 DA rats, and were followed immediately by intrap eritoneal injections of MK-801 (2 mg/kg) or saline. The animals were k illed after 3, 20, or 60 days and the retinal lesions were evaluated h istologically and morphometrically. Results. Photoreceptor-cell loss w as significantly less in MK-801-treated rats than in control animals. The proliferative membrane composed of retinal pigment epithelial cell s and neovascular blood vessels, which was seen at the base of the les ion in control group retinas, was smaller in the MK-801-treated retina s. In rats treated with a higher dose of MK-801, the lesions showed al most no proliferative reaction. Conclusions. A potent noncompetitive N MDA-receptor blocker, MK-801 exhibits neuroprotective and antiprolifer ative properties in the retina. Glutamate-receptor blockers should be investigated further as potential adjuvant therapy in retinal photocoa gulation treatments.