NO donors and experimental retinal branch vein occlusion

Purpose: The development of extended territoires of nonperfused capillaries after branch vein occlusion (b.v.o.) is correlated to the secondary constriction of the arteriole crossing the occluded territory. Local NO release is impaired soon after b.v.o. and accounts for the secondary arteriolar constriction. In this report we present evidences showing that administration of an NO donor can reverse the secondary arteriolar vasoconstriction observed after b.v.o. Material and methods: Simultaneous preretinal NO profiles and arteriolar diameter measurements were performed in miniature pigs after experimental b.v.o., The effect of preretinal microinjections of the NO-donor Sodium Nitroprusside on the arteriolar diameter was studied. Results:A significant arteriolar vasoconstriction occurring in parallel with a preretinal [NO] decrease was observed 4 hours after b.v.o.. Microinjection of the NO-donor SNP caused a segmental, reversible arteriolar dilatation. Conclusion:The present results, suggest that local NO supply in the first hours following b.v.o. may contribute to protect the retina against ischemic injury.