Ischemia-Reperfusion Causes Exudative Detachment of the Rabbit Retina

PURPOSE. To characterize the activation of macroglial (Muller) and microglial cells, as well as neuronal cell degeneration, during ischemia-reperfusion in rabbit retina and to test the possible effect of triamcinolone acetonide on gliosis. METHODS. Transient retinal ischemia was produced by increasing intraocular pressure for 60 minutes. Triamcinolone (8 mg) was intravitreally applied immediately after the cessation of ischemia. At 3 and 8 days after reperfusion, the K + currents of acutely isolated Muller cells were recorded, and the Ca 2+ responses of Muller cells on stimulation of P2Y receptors were recorded fluorometrically in retinal wholemounts. Microglial/ immune cells in the nerve fiber layer of retinal wholemounts were labeled with isolectin. To evaluate neuronal and Muller cell loss, the numbers of cells were counted in retinal slices. RESULTS. Transient ischemia caused exudative detachment of the central retina that was characterized by disruption of the pigment epithelial monolayer, the presence of scattered pigment epithelial and immune cells in the expanded subretinal space, and retinal folds. A significant loss of photoreceptor cells was observed at 8 days after reperfusion. At 3 and 8 days after reperfusion, Muller cell gliosis was apparent, as indicated by cellular hypertrophy, downregulation of K + channel expression, and an increased number of cells that displayed P2Y receptor-mediated Ca 2+ responses. The number of microglial/ immune cells increased strongly after reperfusion. Intravitreal triamcinolone did not affect the parameters of Miiller cell gliosis but decreased the number of microglial/immune cells. CONCLUSIONS. Ischemia-reperfusion of the rabbit retina causes exudative retinal detachment that is characterized by a loss of photoreceptor cells, whereas the inner retina remains largely preserved. Micro- and macroglial cells are activated early during reperfusion, even before dropout of the photoreceptor cells. Intravitreal triamcinolone may decrease the degree of microglial/immune cell activation.