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JE Fries, TH Wheeler-Schilling, E Guenther, K Kohler; Metabotropic P2Y Receptors in the Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1443.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Extracellular purines and pyrimidines modulate a wide variety of physiological responses through the activation of a family of G protein-coupled receptors, referred to as P2Y receptors. Only limited information is available about the retinal distribution of these receptors. Here we report the occurrence and cellular distribution of four subtypes of the P2Y receptors (P2Y1, P2Y2, P2Y4, P2Y6) on the mRNA and protein level in the rat retina. Methods: RT-PCR was used to test for the expression of P2Y1, P2Y2, P2Y4 and P2Y6 in the rat retina (Brown Norway). In addition, single-cell RT-PCR was applied to three distinct cell populations (Retinal Ganglion Cells (RGCs), Bipolar Cells (BPCs) and Müller Cells (MCs)) to analyse the cellular distribution pattern of the P2Y subtypes. cDNA probes of all four P2Y subtypes were used for in situ hybridization (ISH) on retinal sections of different developmental stages (P3-P44). Antibodies raised against P2Y1, 2,and 4 were used for the cellular localisation by immunohistochemistry. Results: RT-PCR revealed the presence of P2Y1, P2Y2, P2Y4 and P2Y6-mRNA in the neural retina and RPE/choroid. By ISH, labeling was detected in the ganglion cell layer (GCL) and in the inner nuclear layer (INL) for subtypes P2Y1,4 and 6 in different intensities. However, the P2Y2 receptor subtype was found only in the GCL, but not the INL. Immunoreactivity for P2Y1, 2 and 4 was found in the GCL, INL and outer plexiform layer (OPL). Additionally, for the P2Y4 receptor three broadly stained sublayers could be distinguished in the inner plexiform layer (IPL). SC-RT-PCR revealed a distinct expression profile of P2Y receptors in different cell types (each n=10): RGCs (P2Y2: 100%; P2Y1: 80%; P2Y6: 50%; P2Y4: 30%); BPCs (P2Y6: 80%; P2Y1: 60%; P2Y2: 40%; P2Y4: 20%); MCs (P2Y6: 100%; P2Y2: 80%; P2Y1: 60%; P2Y4: 60%). Conclusion: Our data strongly suggest the expression of a broad spectrum of metabotropic P2Y receptors within the retina in distinct cell populations, both on the mRNA and protein level. Therefore, it is likely that extracellular nucleotides play complex roles as autocrine or paracrine mediators and also may have neuromodulatory influences on information processing in the retina.
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