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K. Kozaki, A. J. Vingrys, B. V. Bui; Inner Retinal Function in Diabetic Rats Following IOP Elevation. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5901.
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We consider the effect of intra ocular pressure (IOP) elevation on retinal function of diabetic rats.
ERG responses were measured (-6.08 to 1.92 log cd.s.m-2) in anaesthetized (60:5 mg/kg ketamine:xylazine) dark-adapted (> 12 hours) adult Sprague-Dawley rats at 11 weeks following treatment with streptozotocin (STZ, n = 12, 50 mg/kg at 6 weeks of age) or citrate buffer (n = 12). STZ treated animals were given 2 units of insulin daily. One each of each animal underwent anterior chamber cannulation ad IOP elevation to 70 mmHg for 1 hour. ERG responses were analysed to give an index of photoreceptor (a-wave), ON-bipolar (b-wave), amacrine (oscillatory potentials, OPs) and ganglion cell (positive scotopic threshold response, pSTR) function. For each animal the IOP affect was expressed relative to the amplitude of the contralateral uncannulated eye. Two-way repeated measure ANOVA was employed to compare treatment effect across time, with Bonferroni post-hoc tests used at selected time points. Unpaired t-test was used to compare with amplitude and time.
Photoreceptoral (a-wave, control +4 ± 3%, STZ +4 ± 5%) and ON-bipolar cell (b-wave, control +4 ± 3%, STZ +4 ± 5%) mediated responses were not significantly affected by IOP elevation in either control or STZ animals. Similarly, the OPs, which involves amacrine cell activity (OPs, control +28 ± 23%, STZ +18 ± 17%) were not reduced one week after IOP challenge. On the other hand, IOP challenge significantly reduced the ganglion cell dominated pSTR (-36 ± 10%, P = 0.0161) in STZ animals, but had little effect in controls (+11 ± 15%). The negative component of the STR was also unaffected by IOP challenge.
The ganglion cell dominated pSTR was affected following IOP elevation in STZ rats, but not control rats. These data indicate that ganglion cells in diabetic rats are more susceptible to IOP elevation.
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