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S. Mayor-Torroglosa, A. Garcia, M.P. Lafuente, M.P. Villegas-Pérez, P. De La Villa, M. Vidal-Sanz; Correlative Electrophysiological and Anatomical Studies on the Effects of Retinal Ischemia on the ERG and Orthograde Axonal Transport: Neuroprotection with Brimonidine . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5223.
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Purpose: To investigate the effects of transient ligature of the ophthalmic vessels (LOV) with functional techniques. Methods: In adult rats 90 minutes of ischemia were induced by transient ligature of the left ophthalmic vessels (LOV). One hour before ischemia the left eye was treated with two drops of saline alone (vehicle group) or saline containing 0,5% brimonidine (BMD-group). To determine the effects of retinal ischemia on the outer retina, ERG a- and b-wave amplitudes were recorded from both eyes 1, 8 or 12 weeks after LOV. Light flashes of intensities ranging 0,01 to 10 Cd/m2 were presented for 5 ms, from light emission diodes located 5 mm from the cornea, centered on the visual axis. To asses orthograde axonal transport, the orthogradely transported tracer cholera toxin subunit B (CTB) was injected in the left eye 3 months after LOV, and 5 days later serial coronal sections of the midbrain were obtained in the cryostat and stained for CTB. The extension of areas densely innervated by CTB-labelled RGC terminals in the visual layers of the contralateral superior colliculus (SC) was determined with the aid of an image analysis system. Results: ERG a-wave amplitudes in vehicle- or BMD-treated animals at 1, 8 and 12 weeks represented 80 or 93%, 65 or 78% and 43 or 80%, respectively, of control values. ERG b-wave amplitudes in vehicle- or BMD-treated animals at 1, 8 and 12 weeks represented 73 or 96%, 50 or 70% and 44 or 78%, respectively, of control values. The vehicle-treated rats showed large areas devoid of CTB-labelling of the visual layers in the right SC, while BMD treated rats showed a qualitative near to normal density of CTB-labelled RGC terminals spanning the visual layers of the contralateral SC. Conclusions: BMD protects LOV-induced degeneration of outer retinal layers and retino-tectal projection.
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