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M. Hernandez, M. Rivas, E. Fernandez, M. Bongard, D. Rodriguez, E. Vecino; Molecular and Functional Alterations in Rat Retinas During Different Periods of Elevated Intraocular Pressure (IOP): Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5484.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the changes in the expression of specific molecular markers in rat retinas after 1 week, 4 weeks and 20 weeks of elevated IOP and to study the electrophysiological changes of the retinal ganglion cells (RGCs).
Left eyes were operated by cauterizing 3 episcleral veins in order to increase the IOP, while the right eye was used as control. After different periods of elevated IOP, the animals were euthanatized and the retinas fixed and processed for immunohistochemistry by using specific molecular markers for outer retina (M/L opsin and S opsin), inner retina (Goα, PKC, Calcium binging proteins, TH, ChAt, Synaptophysine and BDNF) and glial cells (GFAP and Vimentin). In addition, after 20 weeks of elevated IOP, the retinas of three rats were freshly isolated and placed in a millipore filter in a superfusion chamber and maintained with oxygenated physiological solution. The RGCs were stimulated with light at different intensities and space/temporal patterns. Extracellular recordings were obtained using a rectangular array of 100, 1.5 mm long electrodes (Utah array). All the selected channels of data plus one stimulus channel were digitized with a commercial multiplexed data acquisition system (Bionic Technologies Inc.) and stored for later analysis.
In all periods analyzed we found a decrease in the expression of molecular markers in a subpopulation of amacrine, rod bipolar cells and RGCs. Moreover, after 20 weeks of elevated IOP we found increased synaptophysine expression and after 1 week we also found alterations in glial markers. The electrophysiological studies show no relevant changes occurring in the RGCs pattern of responses; however, we found significant changes in their receptive field size.
The elevated IOP causes small alterations in the electrophysiology of the RGCs but induces significant changes in the molecular expression of different markers of retinal cells that contact directly or indirectly with the RGCs.
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