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N. Brecha, R. Espinoza, A. Vila, S. Schulz; Somatostatin Subtype Receptor 1 Expression in Mouse and Rat Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3068.
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Purpose: Somatostatin (somatotropin releasing-inhibitory factor, SRIF) is a potent neuropeptide that has a widespread tissue distribution, localized to endocrine cells and to neurons in the peripheral and central nervous system. In mouse and rat retinas, SRIF immunoreactivity is localized to a small number of widely spaced amacrine cells in the inner nuclear layer (INL) and displaced amacrine cells in the ganglion cell layer (GCL). The cellular actions of SRIF in mammals are mediated through a family of G-protein-coupled receptors, sst1-5 receptors. We characterized the expression and cellular localization of sst1 receptor in mouse and rat retinas. Methods: Rat and mouse retinas were fixed with 4% paraformaldehyde and processed for indirect immunofluorescence using an affinity-purified antibody against the C-terminus of sst1 receptor raised in rabbits. Antibody specificity was evaluated by immunostaining with the sst1 receptor antibody preadsorbed with 10-6M C-terminus sst1 receptor peptide. Messenger RNA (mRNA) was isolated and first-strand cDNA synthesized using the Micro-FastTrack 2.0 kit (Invitrogen). Sst1 receptor primers were designed from the rat sequence (sense: 1040-1062, antisense: 1272-1293). Results: Specific sst1 receptor immunoreactivity was localized to ganglion cells and amacrine cell bodies, which gave rise to processes into the IPL. These processes ramified narrowly in lamina 3 of the inner plexiform layer (IPL). Immunostaining was near or at the plasma membrane of immunostained cells. Immunostaining was also localized to blood vessels walls, retinal pigment epithelium and the ciliary epithelium layers. Immunostaining was absent in sections incubated with sst1 receptor antibodies preadsorbed with sst1 C-terminus peptide. RT-PCR experiments on rat and mouse retina confirmed expression of sst1 receptor message. Conclusion: These findings indicate that the sst1 receptor is widely expressed in the eye including the retina and ciliary body. These observations indicate a widespread action for SRIF in the eye, including visual image processing in the inner retina, retinal blood flow regulation and fluid secretion modulation of the ciliary body.
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