PROTECTIVE ROLE OF EXCITATORY AMINO-ACID ANTAGONISTS IN EXPERIMENTAL RETINAL ISCHEMIA

Background: Excitatory amino acids and their analogues (NMDA, kainate and AMPA) are implicated in the pathogenesis of ischemic brain injury. In order to fully understand their involvement in the pathogenesis of retinal ischemic injury, we studied the electrophysiological and hist opathological effects of two excitatory amino acid antagonists, cis-PD A and MK 801, in an experimental retinal ischemia model. Methods: The two antagonists were injected intravitreously 15 min before ischemia w as induced by elevatory intraocular pressure caused by external compre ssion. Electrophysiological and histopathological evaluation was made 48 h after 45 min transient ischemia. Results: The excitatory amino ac id antagonists cis-PDA and MK 801 can partially protect against retina l ischemic injury; whereas the mean post-ischemic b-wave amplitude cor responded to 41% of the pre-ischemic value in the control group, it wa s 64% (P = 0.003) and 59% (P = 0.005) following administration of cis- PDA and MK 801 respectively. Histopathological study corroborated thes e data, showing significant differences for morphometric parameters (P = 0.011 and P = 0.007 respectively). Conclusion: These preliminary re sults suggest the possibility of limiting excito-toxicity, one of the lesion-forming mechanisms in ischemic retinal injury.