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Alistair J. Barber, Melissa A. Bridi, Brittany N. Weibley, Penn State Hershey Eye Center; Loss Of Photopic Visual Sensitivity In Streptozotocin-diabetic Long-Evans Rats. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5970.
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© ARVO (1962-2015); The Authors (2016-present)
Streptozotocin (STZ)-diabetic rats have been used extensively to model the early stages of diabetic retinopathy. There is abundant evidence of the consequences of hyperglycemia to the biochemistry and morphology of the retina in this model. There is little documentation, however, of the effect of diabetes on visual function in the STZ-rat. Therefore the aim of this study was to test the hypothesis that diabetes reduces photopic contrast sensitivity and spatial frequency threshold in STZ-diabetic Long-Evans rats.
Male Long-Evans rats were made diabetic by injection with streptozotocin (65 mg/kg, pH 4.5, i.p.). The rats were housed in pairs and weight and blood glucose were tracked on a weekly basis. Contrast sensitivity and spatial frequency threshold were measured 2 and 7 weeks after diabetes induction, using the OptomotryTM optokinetics testing equipment. After 13 weeks the rats were sacrifice and the amount of retinal apoptosis was measured using a cell death ELISA. All statistical comparisons were made using Student’s t-test with p<0.05 considered a significant difference.
Two weeks after induction the STZ-diabetic rats had significantly lower contrast sensitivity compared to age-matched control rats (p<0.01) but there was no significant difference in spatial frequency threshold. After 7 weeks of hyperglycemia both contrast sensitivity and spatial frequency threshold were significantly lower in the STZ-diabetic rats compared to controls (p<0.001). The amount of retinal apoptosis was significantly higher in STZ-diabetic rats, compared to controls (p<0.05).
These data show that visual function is compromised soon after the onset of diabetes in Long-Evans rats. The earliest visual deficit was in photopic contrast sensitivity, which is compromised within the first month of hyperglycemia. The vision loss after 7 weeks was accompanied by increased retinal apoptosis. The Long-Evans STZ-diabetic rat offers an excellent animal model of visual function deficits due to diabetes.
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