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Rachael S. Allen, Iqbal Sayeed, Heather A. Cale, Katherine C. Morrison, Machelle T. Pardue, Jeffrey H. Boatright, Donald G. Stein; The Effects Of Filamentous Occlusion Of The Middle Cerebral And Ophthalmic Arteries On Visual Function. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6056.
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Filamentous occlusion of the middle cerebral artery (MCAO) in rodents is one of the most common models used to study cerebral ischemia and potential treatments. Because of the proximity of the middle cerebral artery and the ophthalmic artery, the insertion of the filament into the internal carotid physically blocks both arteries, a fact seldom acknowledged by studies using this model. We therefore aimed to better characterize deficits in visual function following filamentous occlusion.
Filamentous occlusion surgery was performed on male Sprague-Dawley rats. A filament was inserted through an incision in the external carotid artery and slid into the internal carotid artery so that it blocked the right middle cerebral and ophthalmic arteries. After 90 minutes the filament was removed and reperfusion occurred. Electroretinograms were performed at 2 and 9 days post occlusion with naïve animals serving as controls. Occlusions were designated as severe or moderate based on survival status.
Two days after surgery, rats with severe occlusions showed a significant reduction (52-62%) in dark-adapted b-wave, a-wave, and summed oscillatory potential (OP) amplitudes in affected eyes (n = 3) compared with controls (n = 10; p < 0.05). Meanwhile, rats with moderate occlusions showed a significant delay in dark-adapted b-wave, a-wave, and summed OP implicit times as well as light-adapted b-wave implicit times in affected eyes (n = 4) compared with controls (n = 10; p < 0.01). No significant changes in any ERG parameters were observed at 9 days post surgery.
Filamentous occlusion surgery resulted in decreased visual function. Severe occlusions resulted in loss of amplitude, which might indicate retinal cell death. Moderate occlusions resulted in temporary delays in retinal function that recovered by 9 days post surgery. Stroke models that reduce blood flow to the eye should consider potential visual deficits, especially if behavioral tasks requiring visual function are used to assess the extent of an MCAO injury.
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