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At least 811 records · Page 45Linked to original sources
PubMed2006

Effect of endothelin dual receptor antagonist on VEGF levels in streptozotocin-induced diabetic rat retina.

Diabetic retinopathy (DR), one of the most serious causes of blindness, is often associated with the upregulation of vascular endothelial growth factor (VEGF) in retina. Recently, leukocyte adhesion (leukostasis) is blamed for the occlusion of retinal capillary vascularity, which ultimately contributes to the progression of diabetic retinopathy. In addition, intercellular adhesion molecule-1 (ICAM-1), a representative factor for leukostasis, is increased in the diabetic retina. Endothelin (ET)-1, a potent vasoconstrictor peptide, is deeply linked to the pathogenesis of diabetic retinopathy. Different therapeutic interventions concerning VEGF have already been proposed to prevent diabetic retinopathy. However, no study yet has reported whether ET-1 dual receptor antagonist could alter the upregulated VEGF and ICAM-1 levels in the diabetic retina. The present study investigated the effect of ET(A/B) dual receptor antagonist (SB209670; 1 mg/rat/day) on the expression of VEGF and ICAM-1 in the diabetic rat retina. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ; 65 mg/kg) in Sprague-Dawley rats, whereas control rats (non-DM control) received only citrate buffer. After 1 week, the STZ-administered rats were randomly divided into two groups: one group (DM+SB209670) received ET(A/B) dual receptor antagonist for 2 weeks, and a vehicle group (DM+vehicle) was treated only with saline. After the treatment period, the retinas were removed from the eyeballs. In DM+vehicle group, the VEGF expression of the retinas was significantly increased (32.8 pg/mg) in comparison to that in the non-DM control group (26.2 pg/mg); this upregulation of VEGF was reversed in the DM+SB209670 group (28.6 pg/mg). The expression of retinal ICAM-1 was increased in the DM+vehicle group (152.2 pg/mg) compared with the non-DM control group (121.6 pg/mg). However, SB209670 treatment did not alter the expression of retinal ICAM-1 level (154.8 pg/ml) in DM rats. Thus we conclude that an ET(A/B) dual receptor antagonist could reverse the expression level of VEGF in the diabetic retina while failing to normalize the upregulated ICAM-1 expression.

Animals↗
PubMed1999

Hypoxia inducible factor-1alpha is increased in ischemic retina: temporal and spatial correlation with VEGF expression.

PURPOSE: Hypoxia inducible factor-1 (HIF-1) is a transcription factor composed of HIF-1alpha and HIF-1beta subunits. HIF-1 transactivates multiple genes whose products play key roles in oxygen homeostasis, including vascular endothelial growth factor (VEGF). This study was designed to determine whether HIF-1 levels are increased in ischemic retina and whether there is a correlation with increased expression of VEGF. METHODS: C57BL/6J mice were killed at time points that span retinal vascular development (PO to adult), or on postnatal day (P) 7 they were placed in a 75% oxygen environment for 5 days and then removed to room air and killed after 0, 2, or 6, or 24 hours and 5 or 14 days. Eyes were frozen, and retinas were isolated and used for immunoblot analysis, or eyes were sectioned for immunohisto chemical staining for HIF-1alpha or HIF-1beta, or for in situ hybridization for VEGF. RESULTS: Immunoblots of retinal lysates showed low levels of HIF-1alpha at PO that were markedly increased at P4, remained high throughout the period of retinal vascular development and then decreased to an intermediate level in adults. HIF-1beta levels were relatively constant at all time points. In mice with oxygen-induced ischemic retinopathy, HIF-1alpha levels were increased in the retina. The peak of increase occurred at 2 hours, and levels returned to baseline by 24 hours. Immunohistochemistry showed increased staining for HIF-1alpha throughout the hypoxic inner retina, but not in the normoxic outer retina. There was no modulation of HIF-1beta levels. There was constitutive expression of VEGF mRNA in the inner nuclear layer that was increased 6 hours after the onset of hypoxia and remained elevated for several days. CONCLUSIONS: There are increased levels of HIF-1alpha in ischemic retina that show temporal and spatial correlation with increased expression of VEGF. These findings are consistent with the hypothesis that HIF-1 plays a role in upregulation of VEGF in ischemic retina.

Aging↗
PubMed2003

Light scatter causes the grayness of detached retinas: implications for vision loss in retinal detachment.

OBJECTIVE: To investigate the cause of the gray appearance of the detached retina. METHODS: The effects of ex vivo bovine retinas and Scotch (3M, Minneapolis, Minn) tape on light scattering were predicted based on mathematical modeling and examined empirically on an optical bench. Images were collected with a CCD [charged-coupling device] camera connected to a microcomputer with an image grabber. The clarity of the image was calculated as the standard deviation, sigma. RESULTS: Calculations predicted a gaussian distribution of laser light scattering with increased diffusion with increasing distance from the medium to the target. The image clarity, sigma, increased rapidly in the first 50 micro m of separation of the retina and tape from the test target and the rate of increase diminished thereafter. Removal of the outer retina with an excimer laser improved retinal transparency. CONCLUSIONS: Data explain that the gray appearance of the detached retina results from light scattering. This phenomenon likely results, at least in part, because of the irregular outer retinal surface at the level of the photoreceptors. Clinical Relevance The findings suggest that visual loss in retinal detachment may result, in part, from optical properties of the detached retina and have implications for visual recovery and subretinal surgery.

Animals↗
PubMed1996

Maturational gradients in the retina of the ferret.

In the present set of studies, we have examined the site for the initiation of retinal maturation in the ferret. A variety of maturational features across the developing inner and outer retina were examined by using standard immunohistochemical, carbocyanine dye labelling, and Nissl-staining techniques, including 1) two indices of early differentiation of the first-born retinal ganglion cells, the presence of beta-tubulin and of neuron-specific enolase; 2) the receding distribution of chondroitin sulfate proteoglycans within the inner retina; 3) the distribution of the first ganglion cells to grow axons along the optic nerve; 4) the emergence of the inner plexiform layer; 5) the emergence of the outer plexiform layer and 6) the onset of synaptophysin immunoreactivity within it; 7) the differentiation of calbindin-immunoreactive horizontal cells; and 8) the cessation of proliferative activity at the ventricular surface. Although we were able to define distinct maturational gradients that are associated with many of these features of inner and outer retinal development (each considered in detail in this report), with dorsal retina maturing before ventral retina, and with peripheral retina maturing last, none showed a clear initiation in the region of the developing area centralis. Rather, maturation began in the peripapillary retina dorsal to the optic nerve head, which is consistent with previous studies on the topography of ganglion cell genesis in the ferret. These results make clear that the order of retinal maturation and the formation of the area centralis are not linked, at least not in the ferret.

Animals↗
PubMed1999

Neurotrophins and their receptors in the tench retina during optic nerve regeneration.

To understand the role of neurotrophins in the visual system, we investigated the distribution of both neurotrophins and their receptors within the retina of a fish that has the capacity to spontaneously regenerate its optic nerve axons after lesion. Intact retinas and retinas from tench, whose optic nerve had been crushed, were analyzed by immunohistochemistry and in situ hybridization. Trk receptors were mainly immunolocalized in cells of the inner nuclear and ganglion cell layers, a distribution coincident with that of their mRNAs. Nerve growth factor (NGF) immunoreactivity was detected exclusively in Müller cell processes, and brain-derived neurotrophic factor (BDNF) was found in both neuronal bodies and Müller cell processes. Neurotrophin-3 (NT-3) was detected in most of the cell nuclei, and neurotrophin-4/5 (NT-4/5) was localized in fibers and in a few cells in the inner retina. An increase in both TrkA protein and mRNA was detected during axonal regeneration within the retinal ganglion cell layer, reaching a maximum 30 days postcrush and returning to normal levels by day 90, when optic nerve regeneration is almost completed in this fish. None of the other neurotrophins and receptors showed appreciable changes. The heterogeneous distribution patterns of neurotrophins and their receptors in fish retina, their differences from the distribution observed in other species, and the TrkA changes after optic nerve crush suggest an important role for these molecules in the normal physiology of the fish retina and during the regeneration process.

Animals↗
PubMed1999

Dopamine D1-receptor immunolocalization in goldfish retina.

Dopamine, a neuromodulator in the vertebrate retina, is involved in numerous functions related to light adaptation. However, unlike in mammals, localization of retinal D1-dopamine receptors in nonmammalian vertebrates has been hampered due to a lack of antisera. To address this problem, an antiserum against the 18 C-terminal amino acids of the goldfish D1 receptor (gfD1r) was generated in chicken eggs and tested in retinae of goldfish and rat, and rat caudate putamen, by using immunoblots and light microscopic immunocytochemistry. No labeling was observed in any tissue or immunoblots with preabsorbed gfD1r antiserum. Immunoblot analysis of goldfish retina revealed a single band at about 101 kDa. The patterns of gfD1r immunoreactivity (gfD1r-IR), found in rat caudate putamen and rat retina were virtually identical to that previously reported with other D1-receptor ligands and antisera. In goldfish retina, gfD1r-IR was most intense over cell bodies in the ganglion cell layer, amacrine cells in the proximal inner nuclear layer (INL), and bipolar cells in the distal INL. Weaker gfD1r-IR was observed over horizontal cell bodies and both plexiform layers. Müller cells and axons of cone photoreceptors were labeled as well. Double labeling showed that all protein kinase C-immunoreactive bipolar cells (ON type) were gfD1r-IR on the soma, axon terminal, and dendrites. All glutamate decarboxylase-immunoreactive (i.e., gamma-aminobutyric acid utilizing) amacrine cells and horizontal cells were gfD1r-IR. Retinal D1r distribution is more extensive than dopamine neuron innervation, but is consistent with physiologic estimates of dopamine function, suggestive of both wiring and volume transmission of dopamine in the retina. The gfD1r antiserum displays cross-reactivity to dopamine receptors in a mammal and a nonmammal and should prove useful in future studies of dopaminergic systems.

Amino Acid Sequence↗
PubMed2000

Retinoid-dependent gene expression regulates early morphological events in the development of the murine retina.

Endogenous retinoids have been implicated in the axial patterning of the embryonic vertebrate retina; however, no studies have directly examined how asymmetric retinoid-dependent gene expression regulates early morphological events in the development of the retina. Here we used a line of indicator mice that possess a retinoid-dependent transgene to examine the relationship between retinoic acid (RA)-dependent gene expression and events occurring during early eye morphogenesis, such as the closure of the optic disc. We found that retinoid-regulated gene expression shifts along the dorsal/ventral axis of the embryonic retina; at embryonic day (E) E11.5 transgene expression is restricted to the neuroepithelium in dorsal retina, and by E14.5 only immature cells located in ventral retina and the dorsal retinal margins demonstrate transgene activation. By manipulating RA levels, we were not only able to systemically alter RA-dependent gene expression along the dorsal/ventral axis, but also to affect retinal morphology. In particular, reducing RA availability resulted in the abnormal closure of the optic fissure. These results indicate that asymmetric levels of RA regulate early RA-dependent gene expression in the eye and demonstrate that the normal pattern of retinoid-dependent gene transcription along the dorsal/ventral axis is critical for the proper development of the vertebrate retina.

Animals↗
PubMed2000

Regulation of FGF soluble receptor type 1 (SR1) expression and distribution in developing, degenerating, and FGF2-treated retina.

The spatial and temporal patterns of expression and content of the fibroblast growth factor (FGF) soluble receptor SR1, a specific inhibitor of FGF, were investigated during embryonic and postnatal development of the retina in Fisher rats. As early as at embryonic day 18 (E18), SR1 mRNA and protein were detected in the retina. SR1 protein was strongly associated with the differentiating ganglion cells and its distribution paralleled the radial pattern of retinal development, from center to periphery. From E18 to postnatal day 5, the levels of both SR1 mRNA and SR1 protein remained constant. Thereafter, they decreased rapidly, by a factor of 5 in the adult retina. SR1 was labeled in the inner nuclear layer, but never in the photoreceptor nuclei. In the neural retina of RCS dystrophic rats, the levels SR1 mRNA and SR1 protein were 2 to 3 times higher than those in the normal congenic controls, before and during photoreceptor degeneration. These results provide the first evidence that a natural FGF inhibitor is regulated during retina development and degeneration and suggest that changes in SR1 content may be involved in the regulation of FGF activities in retina. This was confirmed in vivo in RCS rats, in which delayed photoreceptor apoptosis by intravitreal injection of FGF2 was accompanied by a downregulation of SR1 expression. Dev Dyn 2000;217:24-36.

Animals↗
PubMed1998

Differential distribution of beta-dystroglycan in rabbit and rat retina.

The distribution of the dystrophin-associated glycoprotein complex was investigated in rabbit and rat retina by using the monoclonal antibody 43DAG/8D5, which specifically recognizes beta-dystroglycan, a central component of the complex. In cryostat sections of retinae from both species, the authors observed staining of blood vessels, continuous labeling around the vitreal border, and strong immunoreactivity in the outer plexiform layer (OPL). Electron microscopy showed that the immunoreactivity associated with the vitreal border of the retina was the result of a subcellular concentration of beta-dystroglycan in the endfeet of Müller glial cells. A similar concentration was observed in endfeet of perivascular astrocytes in the region of contact with the capillary basal lamina. In the OPL, beta-dystroglycan was associated with the terminals of both rods and cones. The label was almost exclusively found outside the synaptic area and was particularly strong in the extensions of the photoreceptor terminals protruding into the OPL. In the OPL of the rabbit retina, the authors found additional immunoreactivity associated with the tips of postsynaptic horizontal and bipolar cell processes. These results show that the dystrophin-associated glycoprotein complex is subcellularly concentrated in photoreceptor terminals and glial cell endfeet, and that the rabbit retina differs from the rat retina by the additional expression of this complex in bipolar and horizontal cells.

Animals↗
PubMed1999

Circumferential migration of ameboid microglia in the margin of the developing quail retina.

Central-to-peripheral migration of QH1-positive microglial precursors occurs in the vitrealmost part of the developing quail retina. This study shows that some QH1-positive ameboid cells with morphological features of migrating cells are already present in the margin of the retina before microglial precursors migrating centrally to peripherally arrive in this zone. Because the earlier cells are oriented parallel to the ora serrata, we deduce that some microglial cells migrate circumferentially in the margin of the retina, whereas other microglial precursors migrate from central to peripheral zones. Microglial cells that migrate circumferentially are first seen on embryonic day 6 (E6) and advance in a temporal-to-dorsal-to-nasal direction from the temporoventral quadrant of the retina. When cells migrating centrally to peripherally reach the retinal margin, they meet those migrating circumferentially. From E6 on, some QH1-positive dendritic cells in the ciliary body bear processes that penetrate the retina, where they are oriented circumferentially. These observations suggest that microglial cells that migrate circumferentially in the retinal margin share a common origin with dendritic cells of the ciliary body. Therefore, microglial cells of the quail retina appear to make up a heterogeneous population, with some cells originating from the pecten/optic nerve head area and others from the ciliary body.

Aging↗
PubMed2000

Disabled-1 is expressed in type AII amacrine cells in the mouse retina.

The organization of several laminated structures in the brain is controlled by a signaling pathway activated by Reelin, a large glycoprotein secreted by pioneer neurons in the developing brain. Reelin binds to transmembrane receptors, including VLDLR and ApoER2, and stimulates tyrosine phosphorylation of Disabled-1 (Dab1), which associates with an NPxY motif present in the cytoplasmic domain of the receptors. Disruption of reelin, dab1, or both the vldr and apoer2 genes results in similar cell positioning defects in laminated brain regions including the cerebellum, hippocampus, and cerebral cortex. Although retinal ganglion cells express reelin during development, there is no obvious disruption of cell positioning in the retina of reeler mice. Here, we examine the expression pattern of Dab1 as a first step toward understanding the function of the Reelin signaling pathway in neural retina. Immunohistochemical analysis of the adult retina revealed that Dab1 is expressed in a specific type of amacrine cell. These cells display a narrow dendritic field and they project to two distinct sublaminae within the inner plexiform layer. Dab1 co-localizes with the high-affinity glycine transporter, indicating that these amacrine cells are glycinergic. Cells that express Dab1 are surrounded by dopaminergic fibers originating from wide-field amacrine cells. These features are characteristic of type AII amacrine cells described in other mammalian species. Analysis of the retina at several stages of development revealed that Dab1 is expressed shortly after birth during the time at which AII amacrine cells extend neurites and form synaptic connections in the inner retina. This raises the possibility that the Reelin/Dab1 signaling pathway contributes to formation of intraretinal circuitry in the neural retina.

Animals↗
PubMed2001

Müller cell differentiation in the zebrafish neural retina: evidence of distinct early and late stages in cell maturation.

The vertebrate neural retina is mainly composed of cells of neuroectodermal origin. The primary cell types found in all vertebrate retinas are several categories of neurons and the archetypical retina glial cell the Müller cell. Although the neurons and the single glial cell type of the retina are specialized for very distinct functions, they all have a common developmental origin within the tissue. How the distinctions between cell types, in particular between neurons and glia, arise during embryonic development remains a central issue in neurobiology. In this report, we examine the genesis of Müller glial cells during zebrafish (Danio rerio) eye development. Particular emphasis is placed on the expression of the Müller cell maturation markers carbonic anhydrase and glutamine synthetase. In addition, we report that the HNK-1 monoclonal antibody, which identifies a particular glycoconjugate frequently found on cell surface recognition molecules, also identifies zebrafish retina Müller cells early in development. The expression patterns of these three markers clearly show that the Müller cells mature in stages: HNK-1 labeling and glutamine synthetase arise earlier than carbonic anhydrase expression. In addition, the embryonic zebrafish neural retina is characterized by the presence of amoeboid, carbonic anhydrase-positive microglial cells even before the genesis of retinal neuroectodermal glia. The stepwise maturation of the glia is likely to be indicative of an overall retinal maturational program in which cell differentiation and the expression of certain phenotype-defining gene products may be separately regulated.

Animals↗
PubMed2000

Neuronal nitric oxide synthase immunoreactive neurons in the mammalian retina.

The development of immunocytochemistry has led to a better understanding of synaptic transmission carried out by neuroactive substances in the mammalian brain, including the retina. In the mammalian retina, nitric oxide (NO) is widely accepted as a neuromodulator. Histochemistry based on NADPH-d and immunocytochemistry based on nitric oxide synthase (NOS) have been used to identify the presence of nitric oxide in the mammalian retina. Certain types of amacrine cells and a class of displaced amacrine cells have been labeled consistently in all mammalian retinae studied to date. Other cell types showing NADPH-d reactivity or NOS immunoreactivity varied between species. NADPH-d reactive or NOS immunoreactive amacrine cells may serve as a source of NO for amacrine, bipolar, and ganglion cells in the inner retina, whereas interplexiform cells, bipolar cells, and horizontal cells may serve as a source of NO for the outer retina of mammals.

Animals↗
PubMed2000

Amacrine cells of the anuran retina: morphology, chemical neuroanatomy, and physiology.

Amacrine cells are third-order retinal interneurons, projecting their processes into the inner plexiform layer. Historically, they were not considered as neurons first. By the middle of the 20th century, their neuronal nature was confirmed, and their enormous diversity established. Amacrine cells have been most successfully subdivided into morphological categories based on two parameters: diameter of the dendritic field and ramification pattern in the inner plexiform layer. Works combining anatomy, physiology, and neurochemistry are scarce and in the case of the anuran retina, the situation is even worse. Correlation between morphology, neurochemistry, and physiology is little studied. Here we try to build up a database and pinpoint some of the missing data. Obtaining those could help to better understand retinal function. Sporadic attempts did not make it possible to develop a comprehensive catalog of morphologically distinct amacrine cell types in the anuran retina. The number of morphologically identified amacrine cells currently stands at 16. The list of neurochemically identified distinct cell types can be given as follows: five types GABA-containing cell types with secondary markers and at least one without; two glycinergic cell types and one interplexiform cell where glycine colocalizes with somatostatin; one dopaminergic amacrine cell and also a variant of this with interplexiform morphology; two types of serotoninergic cells; three NADPHdiaphorase-positive cells, one substance P-positive cell type without identified second marker; one CCK-positive cell type without identified second marker and the calbindin positive cells (at least one but potentially more types). This adds up to 19 cell types, out of which two are interplexiform in character. This is more than that could be identified by purely morphological means. Out of Cajal's original 13 amacrine cell types described in the frog retina, 5 parallel unequivocally with neurons defined by neurochemistry. Three others have one close match each, but their exact identity is uncertain. The remaining amacrine cells have more than one potential matches. At the same time, on one hand the amacrine cell named two-layered by Cajal so far has no match among the neurochemically identified amacrine cells. On the other hand, the interplexiform subtype of the dopaminergic cell, the somatostatin-containing glycinergic interplexiform cell, the starburst cell, and the bistratified neuropeptide Y-immunoreactive cell have no match among Cajal's cells. All in all, the number of known amacrine and interplexiform cells now stands at at least 21 in the anuran retina. Physiological characterization of amacrine cells shows that their general features seem to be rather similar to those described in tiger salamander retina. In Xenopus retina, morphologically and physiologically identified amacrine cells responded to light stimulation most frequently with ON-OFF characteristics. Immunhistochemical identification of the recorded and dye injected cells showed that amacrine cells of the "same physiological type" might have different morphology. In other words, amacrine cells with different morphology can respond similarly to illumination. Even so, small differences between almost identical responses may reflect that the cell they stem from indeed belongs to different cell types.

Animals↗
PubMed1993

Molecular control of glutamine synthetase expression in the developing retina tissue.

Glutamine synthetase is a differentiation marker of the neural retina, whose expression is restricted to Müller glia cells, is inducible by glucocorticoids and is dependent on tissue development. The retina tissue acquires the competence to express GS in response to glucocorticoids with development, although the level of hormone binding activity in the cells does not alter with age. Using CAT constructs that are controlled by "simple GRE" promoters we demonstrated that glucocorticoid receptor transcription activity in retina cells increases with development. The increase in receptor activity correlates directly with the increase in inducibility of the glutamine synthetase gene and inversely with the rate of retina cell proliferation. At early developmental ages, when retina cells are still proliferating, the glucocorticoid receptor is transcriptionally inactive and glutamine synthetase expression cannot be induced. Receptor activity increases progressively with development and by day 12, when cell proliferation ceases, competence for glutamine synthetase induction is high. This competence for glutamine synthetase induction can be repressed by overexpressing the oncogene v-src, which stimulates retina cell proliferation. We discuss possible mechanisms for developmental-dependent modulation of glucocorticoid receptor transcriptional activity.

Animals↗
PubMed2004

Comparative morphology of the eye (with particular attention to the retina) in various species of cardinal fish (Apogonidae, Teleostei).

Various parameters of the eye dimension and structure have been compared in 15 species of cardinal fish (Apogonidae), including both nocturnal and diurnal forms, mostly inhabiting rocky habitats in tropical and subtropical regions. In general, in the nocturnal forms the eye and retina are larger than in the diurnal fish of similar dimensions. In the nocturnal species, eye diameter to body length is ca. 12-13%, whereas in the diurnal species it is less than 10%. Retina size in adult fish of the various species varies from 20 mm(2) to 183 mm(2). Cytological examination of the studied retinas revealed that they are composes, additional to rods (20-40 microm), of both bulbous and slender double cones, as well as single cones. These cones form a mosaic comprising four double with one single in the center, a pattern that is less prominent at the periphery of the retina and more so in the fundus. The rod ellipsoids reveal normal mitochondria, whereas the cones bear ellipsoids featuring opaque and unusual, ellipsosome-like mitochondria. The number of rods in a retinas varies from 15 to 128 million, and the number of cones from 460,000 to 5,673,000. As revealed in cardinal fish of similar dimensions, the number of visual cells found in the retina is much higher in the nocturnal than in the diurnal species. The ecological and developmental aspects of the observed phenomena are discussed.

Animals↗
PubMed2004

Vanilloid receptor like 1 (VRL1) immunoreactivity in mammalian retina: colocalization with somatostatin and purinergic P2X1 receptors.

The distribution of vanilloid receptor like1 immunoreactivity (VRL1-IR) in the retinas of rat, cat, and monkey was studied by single- and double-labeling immunocytochemistry. The patterns were similar for all three species in that VRL1-IR was most prominent in the inner plexiform layer, with scattered compact projections to the outer plexiform layer (OPL). VRL1-immunoreactive cell bodies were present throughout the rat retina, represented by amacrine cells in the inner nuclear layer and ganglion cell layer (GCL). In cat and monkey retinas, VRL1-immunoreactive cell bodies were restricted to the GCL in the inferior retina. Occasional cell bodies were associated with retinal blood vessels, but their identity as pericytes, glia, or neurons is uncertain. All VRL1-immunoreactive cells and processes colocalized with somatostatin and purinergic P2X1 receptor-IR but not with tyrosine hydroxylase-IR. VRL1-immunoreactive processes in the OPL did not label with antisera against synaptic vesicle 2 (SV2), suggesting that they were dendritic and did not derive from interplexiform cells. However, VRL1-immunoreactive processes in the far periphery toward the pars plana labeled for SV2, suggesting that these processes were presynaptic. The VRL1-immunoreactive cell bodies in the monkey GCL were not calbindin-immunoreactive, demonstrating that they were not displaced H2 horizontal cells. The VRL1-immunoreactive cells in cat and monkey could represent biplexiform and/or associational ganglion cells that receive input in the OPL throughout the retina and direct output to the far periphery. The presence of P2X1 receptors and vanilloid receptor like 1 protein on somatostatin-containing neurons in mammalian retina adds to the growing complexity regarding the chemical control of retinal function that is likely to include the microcirculation.

Animals↗
PubMed2004

Expression of calcium transporters in the retina of the tiger salamander (Ambystoma tigrinum).

Changes in intracellular calcium concentration, [Ca2+]i, modulate the flow of visual signals across all stages of processing in the retina, yet the identities of Ca2+ transporters responsible for these changes are still largely unknown. In the current study, the distribution of plasma membrane and intracellular Ca2+ transporters in the retina of tiger salamander, a model system for physiological studies of retinal function, was determined. Plasma membrane calcium ATPases (PMCAs), responsible for high-affinity Ca2+ extrusion, were highly expressed in the salamander retina. PMCA isoforms 1, 2, and 4 were localized to photoreceptors, whereas the inner retina expressed all four isoforms. PMCA3 was expressed in a sparse population of amacrine and ganglion neurons, whereas PMCA2 was expressed in most amacrine and ganglion cells. Na+/Ca2+ exchangers, a high-capacity Ca2+ extrusion system, were expressed in the outer plexiform layer and in a subset of inner nuclear and ganglion layer cells. Intracellular Ca2+ store transporters were also represented prominently. SERCA2a, a splice variant of the sarcoplasmic-endoplasmic Ca2+ ATPase, was found mostly in photoreceptors, whereas SERCA2b was found in the majority of retinal neurons and in glial cells. The predominant endoplasmic reticulum (ER) Ca2+ channels in the salamander retina are represented by the isoform 2 of the IP3 receptor family and the isoform 2 of the ryanodine receptor family. These results indicate that Ca2+ transporters in the salamander retina are expressed in a cell type-specific manner.

Ambystoma↗