Effect of Chronic Retinal Hypoperfusion on the Physiology and Morphology of the Visual Pathways of Three Strains of Rats

Abstract

Abstract: : Purpose. To determine the effect of chronic retinal hypoperfusion on the electroretingram (ERG) of three strains of rats, and on the morphological alterations of the visual pathway in Wistar rats.. Methods. Chronic hypoperfusion was induced by bilateral common carotid artery occlusion (BCCAO) in Long-Evans, Sprague-Dawley and Wistar rats. ERGs were elicited by different stimulus intensities at different times after the ligation. Immunohistochemical studies were performed on Wistar rats for astroglial reactions in central visual pathways using antibodies to GFAP. Results. In Long-Evans rats, BCCAO led to a loss of the b-wave within 1 to 7 days in the majority of the animals, and in the Sprague Dawley rats, all components of the ERGs were reduced but a b-wave was still present in most of the animals. In 13 Wistar rats, 7 rats showed a loss of the b-wave (negative-type ERG), 5 had reduced ERGs with all components present, and one was flat. The changes in the two eyes were not always symmetrical. Ten of ten Wistar rats had reactive astrocytes in the optic tract and superior colliculus bilaterally after 1 week survival. Gross atrophy was found in 21/26 optic nerves of Wistar rats surviving for 6 months (n=3 unilaterally) and in 15/18 surviving 12 for months (n=1 unilaterally). Conclusions. These findings indicate that in investigations of retinal hypoperfusion, the strain of rats must be designated. It is important to examine the physiological condition of the retina before conclusions can be made on the morphological changes. Parallel changes may occur in different portions of the visual system after carotid artery occlusion. Supported by NS05820-36S1.

Keywords: retinal degenerations: cell biology • ischemia • electroretinography: non-clinical