Neuropeptide Y Receptors Y₁and Y₂are Present in Neurons and Glial Cells in Rat Retinal Cells in Culture

Abstract

PURPOSE. Neuropeptide Y (NPY) is one of the most abundant peptides in the central nervous system (CNS), including the retina. This peptide activates various different G-coupled receptors (NPY Y 1 , Y 2 , Y 4 , and Y 5 ) that are also present in the retina. However, the localization of NPY receptors in the several types of retinal cells is not completely known. In this study, we have looked at the distribution of NPY Y 1 and Y 2 receptors in rat retinal cells to reveal new perspectives on the role of NPY receptors in retina physiology. METHODS.Rat retinal neural cell cultures were prepared from newborn Wistar rats (P3-P5) and pure rat Müller cell culture was obtained after treatment of these cells with ascorbic acid. 1 This 36-amino acid peptide was first isolated from the pig brain in 1982 by Tatemoto.2 NPY is one of the most abundant peptides in the central nervous system (CNS), including the retina, and is involved in numerous physiologic functions, such as feeding, memory processing, and cognition.3,4 NPY actions are mediated by G protein-coupled receptors, which have been named NPY Y 1 , Y 2 , Y 4 , Y 5 , and y 6 . 3,5 NPY is expressed in the retina of mammals and nonmammals. [6][7][8][9][10][11][12] In rodent retinas, NPY-immunoreactivity (NPY-ir) is present in the inner retina, it is localized in cell bodies at both inner nuclear layer (INL) and ganglion cell layer (GCL), and is also present in processes located in the inner plexiform layer (IPL).11,13 NPY shows one of the highest degrees of phylogenetic preservation, compared with other neuropeptides, and does not show marked differences between species.14,16 From a consideration of the phylogenetic preservation, it is expected that the NPY and NPY receptor distribution in the retina does not vary significantly between species. NPY-ir is present in amacrine cells in the majority of species studied (fish, frogs, lizards, rodents, baboons, pigs, cats, chickens, and pigeons). Cats, dogs, dolphins, and humans also show NPY in their ganglion cells, 9,17-20 while some turtles, lizards, and frogs present NPY-ir in bipolar cells. 8,21,22 Few studies have analyzed the distribution of NPY receptors either in the retina or in specific retinal cell types. The presence of both Y 1 and Y 2 receptors in the mouse retina has been confirmed by mRNA analysis 13,23 ; however, it is unclear which cell types express these receptors. Moreover, in primary cultures of Müller cells isolated from the retina of guinea pig, a functional assay of cell proliferation suggested the presence of NPY Y 1 receptor in these glial cells. 24 In human retinal pigment epithelium (RPE), mRNA encoding for NPY Y 1 , Y 2 , and Y 5 receptors has been detected, while in bovine RPE only mRNAs encoding for NPY Y 1 and Y 2 receptors have been found. 25 Although the presence of NPY receptors in the rat retina has been described, in particular in NPY Y 1 , Y 2 , Y 4 , and Y 5 mRNA expression, 26,27 little is known about their localization. The NPY Y 1 receptor-ir is localized in horizontal and amacrine ce...

Neuropeptide Y system in the retina: From localization to function

“…In several studies NPY-IR was not detected in the ONL of goldfish, killifish, guinea pig, dolphin and dog (Chen et al, 1999;Kang et al, 2001;Osborne et al, 1985;Subhedar et al, 1996). We have recently shown that rhodopsin-positive cells in rat retinal cell cultures are also immunoreactive for NPY Y 1 and Y 2 receptors (Santos-Carvalho et al, 2013a). Moreover, in adult rat retinal slices we confirmed that NPY Y 1 -and Y 2 -IR localizes in the retina ONL (Santos-Carvalho et al, 2013a).…”

“…In relation to the NPY receptors in ganglion cells, we have shown the presence of NPY Y 1 and Y 2 receptors-IR in ganglion cells (Brn3a-positive cells) in rat retinal cell cultures (Santos-Carvalho et al, 2013a). In addtion, both receptors were detected in GCL in rat retinal slices (Santos-Carvalho et al, 2013a).…”

“…The NPY Y 1 -IR puncta was present in palvalbumin-positive cells in rat and monkey retinas, confirming the expression of NPY Y 1 in AII amacrine cells (Jones et al, 2002). Similarly, immunoreactivity to NPY Y 1 and Y 2 receptors was observed in IPL of rat retina (Santos-Carvalho et al, 2013a). Furthermore, in cultured rat retinal cells, NPY Y 1 and Y 2 receptors-IR were also observed in three different sub-populations of amacrine cells: calbindin-, calretinin-and parvalbumin-positive cells (Santos-Carvalho et al, 2013a).…”

“…Moreover, using double-immunostaining with calbindin, a horizontal cell marker, these authors confirmed the presence of NPY Y 1 receptor-IR in horizontal cells . In rat retinal slices, we observed that NPY Y 1 -and Y 2 -IR are present in processes of OPL, as well as in calbindin-positive cells in rat retinal cells in culture (Santos-Carvalho et al, 2013a). Despite these findings, the role of NPY receptors in horizontal cells has not yet been investigated.…”

Adenosine A 3 receptor activation is neuroprotective against retinal neurodegeneration

“…The cells were maintained at 37°C in a humidified atmosphere of 5% CO 2 . These retinal cell cultures are composed of neurons (photoreceptors, bipolar cells, horizontal cells, amacrine cells and RGCs), and glial cells (Müller cells, astrocytes and microglia), as previously described (Santos-Carvalho et al, 2013a).…”