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AA Vugler, NJ Hewson-Stoate, SO J Whiteley, PJ Coffey; Retinal Dopamine Release in the RCS Dystrophic Rat . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3680.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous reports indicate reductions in retinal dopamine (DA) levels and changes in endogenous release of DA in dystrophic rats. To further investigate these issues we will use a novel immunohistochemical technique to examine release and localisation of DA. Method: 13-15 week old pigmented Royal College of Surgeons (RCS) non-dystrophic and dystrophic rats were used in this series of experiments. DA was identified in the retina by immunohistochemistry using an antibody specific for this neurotransmitter. Two series of experiments examined the retinae of these RCS rats: (1) during ambient illumination and (2) during no illumination (ie.,dark cycle). Also in each series, non-dystrophic and dystrophic RCS rats were injected with either saline or alpha-methyl-p-tyrosine (AMPT). AMPT was given to inhibit tyrosine hydroxylase activity thus facilitating visualisation of dopamine release. Results: In non-dystrophic RCS rats in ambient illumination DA immunoreactivity (IR) was confined to amacrine cells (AC) and their processes in the inner plexiform layer (IPL). In particular, fibres were most discernable in the a-sublayer of IPL, with the most intense band of IR seen in the ganglion cell layer (GCL). This pattern of IR was similar in dystrophic retinae, however, a gradient of IR was observed in the IPL (a-sublayer), and GCL increasing in intensity from the inferior to superior retina. After AMPT administration, both non-dystrophic and dystrophic retinae showed dramatic reductions in the level of IR in the a-sublayer. Staining was almost absent here (clear indication of DA release from AC fibres). In the dark condition, the pattern of IR in non-dystrophic and dystrophic retinae appeared similar to that observed in the light-saline groups but less intense. In particular, IR in the IPL was reduced in the inferior retina of dystrophic rats. After AMPT administration in the dark, the major finding was a virtual absence of IR in the a-sublayer of the IPL in the dystrophic group, which was not seen in the non-dystrophic group. Conclusion: This novel technique can be used to visualise retinal DA release in response to light. DA is released from AC in dystrophic retinae in response to light, despite the substantial loss of photoreceptors at the age studied. In the dark, DA release from AC is greater in dystrophic retinae. This may reflect the lack of tonically active photoreceptors in the dark in these animals. The presence of residual photoreceptors in superior regions of the dystrophic retina, may account for spatial variability in changes observed.
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