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Results for “Retinal Horizontal Cells”

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PubMed1993

Immunocytochemical localization of the amino acid neurotransmitters in the chicken retina.

Postembedding immunocytochemistry was used to determine the cellular localization of the amino acid neurotransmitters glutamate, aspartate, gamma-aminobutyric acid (GABA), and glycine in the avian retina. The through retinal pathway was glutamatergic, with all photoreceptors, bipolar cells, and ganglion cells being immunoreactive for glutamate. Bipolar cells displayed the highest level of glutamate immunoreactivity, with the cell bodies terminating just below the middle of the inner nuclear layer. All lateral elements, horizontal cells, amacrine cells, and interplexiform cells were immunoreactive for glycine or GABA. The GABAergic neurons consisted of two classes of horizontal cells and amacrine cells located in the lower part of the inner nuclear layer. GABA was also localized in displaced amacrine cells in the ganglion cell layer, and a population of ganglion cells that co-localize glutamate and GABA. Both the horizontal cells and GABAergic amacrine cells had high levels of glutamate immunoreactivity, which probably reflects a metabolic pool. At least two types of horizontal cells in the avian retina could be discriminated on the basis of the presence of aspartate immunoreactivity in the H2 horizontal cells. Glycine was contained in a subclass of amacrine cells, with their cell bodies located between the bipolar cells and GABAergic amacrine cells, two subclasses of bipolar cells, displaced amacrine cells in the ganglion cell layer, and ganglion cells that colocalize glutamate and glycine. Glycinergic amacrine cells had low levels of glutamate. We have also identified a new class of glycinergic interplexiform cell, with its stellate cell body located in the middle of the inner nuclear layer among the cell bodies of bipolar cells. Neurochemical signatures obtained by analyzing data from serial sections allowed the classification of subclasses of horizontal cells, bipolar cells, amacrine cells, and ganglion cells.

Amino Acids↗

PubMed1985

Immunoreactive somatostatin in the rat retina: light microscopic immunocytochemistry and chromatographic characterization.

The retinas of adult, male Long-Evans rats contain somatostatin-like immunoreactive material (SLI) as detected by radioimmunoassay. The SLI co-chromatographs with synthetic somatostatin-14 on both gel permeation chromatography and reversed phase high performance liquid chromatography; no somatostatin-28-like material or higher molecular weight forms have been detected. Immunocytochemical methods detect SLI in at least two cell populations. The more abundant stained cells are at the inner margin of the inner nuclear layer and give off processes which form a dense meshwork of fine, varicose fibers at the outer border of the inner plexiform layer, as well as processes which pass into other sublaminas of the inner plexiform layer. Varicose immunoreactive fibers run vertically or obliquely through the inner nuclear layer and bifurcate at its outer margin, giving rise to horizontally running fibers in the outer plexiform layer. These observations are consistent with rat retinal SLI being contained within amacrine cells, at least some of which are interplexiform cells. With cholchicine pretreatment, a more sparse population of stained cells is detected in the ganglion cell layer. These cells give rise to processes which enter the inner plexiform layer. It is not known if these are ganglion cells or displaced amacrine cells.

Animals↗

PubMed1999

Differential expression of AP-2alpha and AP-2beta in the developing chick retina: repression of R-FABP promoter activity by AP-2.

Retinal fatty acid binding protein (R-FABP) is the avian counterpart of murine brain FABP implicated in glial cell differentiation and neuronal cell migration. R-FABP is highly expressed in the undifferentiated retina and brain of chick embryos. We have previously shown by in vitro studies that the AP-2 transcription factor binds to a consensus AP-2 binding site in the R-FABP promoter region. Based on the expression pattern of AP-2 in the developing retina and on mutational analysis of the AP-2 binding site in DNA transfection experiments, we proposed that AP-2 could be involved in the down-regulation of R-FABP transcription. Here, we describe the cDNA isolation of two members of the AP-2 family expressed in the chick retina, AP-2alpha and AP-2beta. We show that R-FABP mRNA and the AP-2 factors are expressed in mutually exclusive patterns in the differentiating retina: whereas AP-2alpha and AP-2beta are selectively expressed either in amacrine, or in amacrine and horizontal cells, respectively, R-FABP mRNAis found in Muller glial cells and/or bipolar cells. Furthermore, a decrease in R-FABP-dependent expression is obtained upon cotransfection of primary retinal cultures with AP-2 expression vectors and a CAT reporter construct. The early and cell-specific expression of AP-2alpha and AP-2beta in the developing retina suggest a role for this transcription factor family in the early steps of amacrine and horizontal cell differentiation. Repression of the R-FABP gene in these cells may be an important component of their developmental program.

Amino Acid Sequence↗

PubMed1973

Localization of the violet and yellow receptor cells in the crayfish retinula.

Cellular identification of color receptors in crayfish compound eyes has been made by selective adaptation at 450 nm and 570 nm, wavelengths near the lambda(max)'s of the two retinular cell classes previously demonstrated. By utilizing earlier evidence, the concentration of lysosome-related bodies (LRB) was used to measure relative light adaptation and thus wavelength sensitivity in 665 retinular cells from six eyes. The observed particle distributions demonstrate the following. Both violet and yellow receptors occur ordinarily in each retinula. Of the seven regular retinular cells two (R(3) and R(4) using Eguchi's numbering [1965]) have mean sensitivities significantly greater to violet and less to yellow than the other five. The latter apparently comprise "pure" yellow receptors (R(1) and R(7)) and mixed yellow and violet receptors (R(2), R(5), and R(6)). Explanations of such ambiguity requiring two visual pigments in single retinular cells or intercellular coupling of adjacent neuroreceptors are apparently precluded by previous evidence. Present data imply alternatively some positional variability in the violet pair's location in individual retinulas. Thus R(3) and R(4) are predominantly the violet receptors but in some retinulas R(2) and R(3) or R(4) and R(5) (or rarely some other cell pairs) may be. The retinal distribution of such variations has yet to be determined. In agreement with intracellular recordings the blue and yellow cells here identified belong to both the vertical and horizontal e-vector sensitive channels.

Adaptation, Ocular↗

PubMed2003

Immunohistochemical localization of human pineal tissue antigens in normal retina and retinoblastomas.

The normal human retina and retinoblastomas were examined immunohistochemically to assess the localization of pineal antigens in the retina and the oncogenesis and differentiation of retinoblastoma. In the present study, 41 eyes excised from children (aged 4 months to 7 years, all unilateral occurrence) diagnosed to have retinoblastoma and 4 eyes with normal retinas, were used. Retinoblastomas were histopathologically classified into well-differentiated, moderately-differentiated, and poorly-differentiated types. The antibodies used were 9 monoclonal antibodies to human pineal antigens and 6 antibodies to neural tissues. In the normal retina, staining patterns characteristic of retinal cell layers were observed with PP1, PP3, PP5, PP6, PI1, and PI2 antibodies. In retinoblastomas, PP5 antibody, which reacts with horizontal cells and ganglion cells, and PP6 antibody, which reacts with part of the bipolar cells in the inner nuclear layer, showed intense staining in well-differentiated retinoblastomas, but the intensity of staining and the positivity decreased with the degree of dedifferentiation. Antigens recognized by PP3 and PP4 antibodies were positive in all retinoblanstomas. Reactions to GFAP antibody and antibodies that recognize Müller cells were negative. Retinoblanstomas may express markers of not only photoreceptor cells but also other retinal nuclear cells. These results suggest that the retinoblastoma might be developed from visual stem cells, which are common progenitor cells of photoreceptor cells, intermediate neurons, and ganglion cells.

Antibodies, Monoclonal↗

PubMed2004

Potential for neural regeneration after neurotoxic injury in the adult mammalian retina.

It has long been believed that the retina of mature mammals is incapable of regeneration. In this study, using the N-methyl-D-aspartate neurotoxicity model of adult rat retina, we observed that some Müller glial cells were stimulated to proliferate in response to a toxic injury and produce bipolar cells and rod photoreceptors. Although these newly produced neurons were limited in number, retinoic acid treatment promoted the number of regenerated bipolar cells. Moreover, misexpression of basic helix-loop-helix and homeobox genes promoted the induction of amacrine, horizontal, and rod photoreceptor specific phenotypes. These findings demonstrated that retinal neurons regenerated even in adult mammalian retina after toxic injury. Furthermore, we could partially control the fate of the regenerated neurons with extrinsic factors or intrinsic genes. The Müller glial cells constitute a potential source for the regeneration of adult mammalian retina and can be a target for drug delivery and gene therapy in retinal degenerative diseases.

Aging↗

PubMed1985

Velocity sensitivity and directional selectivity of frog retinal ganglion cells depend on chromaticity of moving stimuli.

Action potentials of single afferent optic-nerve fibers were recorded in the superficial layers of the optic tectum of frogs. Horizontally moving chromatic stimuli were applied. A large range of stimulus velocities and 2 or 3 different wavelengths (450, 500 or 580 nm) of the moving monochromatic light spots were applied. The velocity functions of class 3 neurons varied only slightly with different chromatic stimuli. About half of the neurons of our sample exhibited directional selectivity to one or two of the wavelengths investigated. In some of these neurons the directional selectivity was found over the entire velocity range studied (0.046-18.4 degrees X s-1), while in others it was also dependent upon the angular velocity of the moving chromatic spot. Thus, a new principle of chromatic-signal processing exists in frogs which has so far not been described in other animals: an interrelation between directional selectivity, chromatic composition of the stimulus and angular velocity. We concluded from these findings that the analytic properties of tectal cells, with respect to their possible function in pattern recognition, might receive insufficient description when the stimuli are restricted to the achromatic grey scale. On the other hand, we would like to stress that the peculiar properties of the retinal color channels in frogs, directional selectivity and different time constants of the recovery functions, contribute to the processing of black/white stimuli according to their shape, size and velocity, since the response to the leading edge and the trailing edge traversing the receptive field depends on these factors.

Animals↗

PubMed1986

Staining of retinal neurons in the isolated eyecup by extracellular horseradish peroxidase injection.

A reliable method has been developed for the staining of mammalian retinal neurons in the isolated eyecup. Small injections of horseradish peroxidase are made at a number of places on the retinal surface while the hemisected eyecup preparation floats in Eagle's medium. After 30 min, the retinas are removed, fixed, and reacted with diaminobenzidine. Golgi-like staining of fine dendrites, spines and axons of ganglion cells is achieved. The method also stains amacrine, horizontal and bipolar cells.

Animals↗

PubMed1988

Glutamate-induced K+ flux in the photoreceptor layer of isolated retina of cyprinid fish: possible consequences for second-order neurones.

The effect of L-glutamate on extracellular K+ activity (aK0) in the micro-environment of the isolated retina of a cyprinid fish was investigated using double-barrelled K+-sensitive micro-electrodes. Glutamate was pulsed onto the retina from an atomizer, and aK0's recorded at different retinal depths. Glutamate induced a concentration-dependent rise in aK0 which was maximal in the first 100 microns of the retinal surface. The aK0 change was transient, with a time to peak of 20-30 s, and complete reversal within 4 min. However, if the retina was pre-treated with dinitrophenol or ouabain, the maximum rise in aK0 was greater than normal, and the effect was sustained. Application of equimolar glutamate transiently depolarized the membrane potentials of horizontal cells. The effects of glutamate on aK0 and horizontal cell membrane potential had some common characteristics. It is concluded that glutamate may have non-synaptic effects on post-receptoral retinal neurones, and possible mechanisms of this are considered.

Animals↗

PubMedDate not supplied

Dynamic changes in the receptive fields of L1-type horizontal cells in the retina of the turtle Mauremys caspica.

The resistances of the horizontal cell syncytium in the vertebrate retina are modulated in a time-dependent fashion during light stimulation. Therefore, the spatial properties of horizontal cells are expected to change with time after the illumination conditions are altered. This study was designed to investigate time- and intensity-dependent changes in the receptive-field properties of L1-type horizontal cells in the turtle Mauremys caspica. Photoresponses were elicited by monochromatic (650 nm) light stimuli of 2-s duration covering retinal spots of different radii. The length constants were derived from the relationships between amplitude and spot radius that were constructed for different time intervals after onset of the light stimulus. For a given stimulus intensity, the length constant transiently increased to a peak value and then slowly recovered to a plateau level. When the length constant was compared to the amplitude of the response to full-field illumination for the entire duration of the light stimulus, an ellipse-like curve was obtained indicating that for a given membrane potential, two different values of the length constant could be obtained. Dopamine considerably reduced the size of the receptive fields but did not affect the time-dependent changes in the length constant. These results indicate that changes in the membrane resistance underlie short-term modulation of the receptive-field properties of turtle L1-type horizontal cells after onset of a light stimulus.

Animals↗

PubMed1987

Quantitative morphology of the primate peripheral retina (Macaca irus).

By using electron microscopy to study the quantitative morphology of the retina, it was possible to determine the spatial density of all principal retinal cells at a defined retinal location. In two retinas of cynomolgus monkeys at a position of 30 degrees nasal of the fovea centralis, the following cell densities were determined from composite electron micrographs: retinal pigment epithelium: 3,400 cell/mm2; rod cells: 115,000 and 168,000 cells/mm2; cone cells: 8,200/mm2; horizontal cells: 7,000/mm2; bipolar cells: 50,000/mm2; amacrine cells: 11,500/mm2; Müller cells: 16,000/mm2; and ganglion cells: 5,350 and 6,750/mm2.

Animals↗

PubMedDate not supplied

Push-pull model of the primate photopic electroretinogram: a role for hyperpolarizing neurons in shaping the b-wave.

Existing models of the primate photopic electroretinogram (ERG) attribute the light-adapted b-wave to activity of depolarizing bipolar cells (DBCs), mediated through a release of potassium that is monitored by Müller cells. However, possible ERG contributions from OFF-bipolar cells (HBCs) and horizontal cells (HzCs) have not been explored. We examined the contribution of these hyperpolarizing second-order retinal cells to the photopic ERG of monkey by applying glutamate analogs to suppress photoreceptor transmission selectively to HBC/HzCs vs. DBCs. ERGs of Macaca monkeys were recorded at the cornea before and after intravitreal injection of drugs. Photopic responses were elicited by bright 200-220 ms flashes on a steady background of 3.3 log scotopic troland to suppress rod ERG components. 2-amino-4-phosphonobutyric acid (APB), which blocks DBC light responses, abolished the photopic b-wave and indicated that DBC activity is requisite for photopic b-wave production. However, applying cis-2,3-piperidine dicarboxylic acid (PDA) and kynurenic acid (KYN), to suppress HBCs/HzCs and third-order neurons, revealed a novel ERG response that was entirely positive and was sustained for the duration of the flash. The normally phasic b-wave was subsumed into this new response. Applying n-methyl-dl-aspartate (NMA) did not replicate the PDA+KYN effect, indicating that third-order retinal cells are not involved. This suggests that HBC/HzC activity is critical for shaping the phasic b-wave. Components attributable to depolarizing vs. hyperpolarizing cells were separated by subtracting waveforms after each drug from responses immediately before. This analysis indicated that DBCs and HBC/HzCs each can produce large but opposing field potentials that nearly cancel and that normally leave only the residual phasic b-wave response in the photopic ERG. Latency of the DBC component was 5-9 ms slower than the HBC/HzC component. However, once activated, the DBC component had a steeper slope. This resembles properties known for the two types of cone synapses in lower species, in which the sign-preserving HBC/HzC synapse has faster kinetics but probably lower gain than the slower sign-inverting G-protein coupled DBC synapse. A human patient with "unilateral cone dystrophy" was found to have a positive and sustained ERG that mimicked the monkey ERG after PDA+KYN, indicating that these novel positive photopic responses can occur naturally even without drug application. These results demonstrate that hyperpolarizing second-order neurons are important for the primate photopic ERG.(ABSTRACT TRUNCATED AT 400 WORDS)

Aminobutyrates↗

PubMedDate not supplied

The gap junction blockers carbenoxolone and 18beta-glycyrrhetinic acid antagonize cone-driven light responses in the mouse retina.

Gap junctions are widely expressed throughout the retina, and play an important role in the processing of visual information. It has been proposed that horizontal cells express unpaired gap junctions, or hemichannels, in their dendrites, and that current flowing through hemichannels reduces transmembrane voltage at cone terminals, promoting the opening of Ca2+ channels near sites of transmitter release. This model predicts that pharmacological block of gap junctions should reduce the Ca2+ current at the equivalent cone voltage, thereby decreasing the postsynaptic light response. To test this prediction, and estimate the relative magnitude of this effect on third-order cells, we recorded light responses in mouse ganglion cells under photopic conditions and applied two gap junction antagonists, carbenoxolone and the structurally related 18beta-glycyrrhetinic acid (GA). Both carbenoxolone and GA decreased the size of the light response to about 30% of control. Cells that were physiologically identified as ON, OFF, or ON/OFF were equally affected by carbenoxolone/GA. These gap junction blockers did not interfere with gamma-aminobutyric acid (GABA) or glutamate receptors, as they did not affect responses to direct activation of these receptors. Under control conditions, spots larger than 200 microm in diameter activated ganglion cell receptive-field surrounds. Comparing responses to small and large spots before and during carbenoxolone treatment, we found that carbenoxolone did not preferentially inhibit surround antagonism at the ganglion cell level, but instead scaled the responses to all spot sizes. Our results extend the findings of studies in lower vertebrates which showed that light responses in horizontal cells are decreased by carbenoxolone treatment, and support the idea that hemichannels in the outer retina, most likely on horizontal cells, constitute important gates that are critical for allowing light responses to move forward into the retinal circuit. Furthermore, it suggests that ganglion cell surrounds are generated in the inner retina.

Animals↗

PubMedDate not supplied

Neural interactions between cone photoreceptors and horizontal cells in the turtle (Mauremys caspica) retina.

Horizontal cells and cone photoreceptors in the vertebrate retina are interconnected by a complex network of synapses leading to the generation of color-coded responses in chromaticity horizontal cells. A simple cascade model of excitatory feedforward and inhibitory feedback synapses had been suggested to underlie these observations. In this study, the photoresponses of cones and horizontal cells were recorded intracellularly from the turtle eyecup. Three different approaches were adopted in order to test quantitatively the cascade model. Comparing linearity functions between these neurons indicated multiple excitatory inputs to each type of horizontal cells. The depolarizing photoresponses of R/G C-type horizontal cells were considerably faster than those of L-type horizontal cells but slower than those recorded from L-cones. This observation disagrees with the basic assumption of the cascade model that assign the depolarizing photoresponses of R/G C-type horizontal cells to a negative feedback pathway from L-type horizontal cells onto M-cones. Finally, the action spectra of each of the three types of horizontal cells could not be solely accounted for by input from one spectral type of cones. Only by assuming excitatory and inhibitory inputs from all spectral types of cones, the action spectra of all types of horizontal cells could be reconstructed. These findings suggest that the negative feedback pathways from horizontal cells onto cones in the turtle retina cannot solely account for the chromatic properties of the horizontal cells and support a direct inhibitory inputs from cones to turtle horizontal cells.

Animals↗

PubMed1987

Rod-cone interactions in night-blinding disease.

When rods are dark-adapted they reduce cone flicker sensitivity as though a low-pass filter had been inserted in the visual pathway. This process is exaggerated in certain individuals and accounts for their complaint of night blindness, though ordinary clinical testing shows no abnormality. This rod-cone interaction occurs in the ERG and is absent in disease of the outer retina, which argues that the pathway involved is via the horizontal cell feedback onto the cones. Various anomalies of rod-cone interaction can be seen in retinitis pigmentosa. These suggest that it is the rod dark current which is responsible for inhibiting cones. The implications for the pathophysiology of retinitis pigmentosa are discussed.

Dark Adaptation↗

PubMed1983

Phosphoinositide metabolism in the retina: localization to horizontal cells and regulation by light and divalent cations.

Isolated retinas from Xenopus laevis incorporated greater amounts of [3H]inositol and 32Pi into phosphoinositides when incubated in light than did control retinas incubated in the dark. Inositol was primarily incorporated into phosphatidylinositol (83-86%), while phosphate labeled the polyphosphoinositides (72-79%). The incorporation of radioactive glycerol, serine, choline, or ethanolamine into retinal lipids was unaffected by light. Following incubation with [3H]inositol, the cell type involved in the light response was identified by light and electron microscope autoradiography to be the horizontal cell. These results are consistent with a classic phosphatidylinositol effect in the retina. An interesting feature of this response is that the stimulus (light) is received in the photoreceptor cell and the effect is manifest in the horizontal cell.

Animals↗

PubMed1983

An analogue model of the luminosity-channel in the vertebrate cone retina. 1. Hardware and responses to square wave voltages.

An analogue simulation was built of the vertebrate cone retina based on the model of Siminoff [J. Theor. Biol. 86, 673 (1980)]. Linear operational amplifiers were used for a few simple processes such as summation, integration (for synaptic delay), inversion and gain. Spatial and temporal properties of retinal elements were developed by interaction of simulated retinal neurons. Tonic and phasic ganglion cells were formed from the center-surround antagonistic receptive fields of bipolar cells. Center field input voltages favored the static levels of tonic units, while surround field input voltages favored the phasic units. Properties of receptive fields of retinal neurons could be simulated by the model using 2 antagonistic input voltages, one of which had a longer synaptic delay. Negative feedback from horizontal cells to cones and its potentiation by electrical coupling of horizontal cells reinforced overshoot produced by surround field input voltages with its extra synaptic delay as compared to the center field input voltage. In spite of simplifications, the model was a good representation of some properties of the retina.

Animals↗

PubMed1997

Neurobiology of retinal dopamine in relation to degenerative states of the tissue.

Neurobiology of retinal dopamine is reviewed and discussed in relation to degenerative states of the tissue. The Introduction deals with the basic physiological actions of dopamine on the different neurons in vertebrate retinae with an emphasis upon mammals. The intimate relationship between the dopamine and melatonin systems is also covered. Recent advances in the molecular biology of dopamine receptors is reviewed in some detail. As degenerative states of the retina, three examples are highlighted: Parkinson's disease; ageing; and retinal dystrophy (retinitis pigmentosa). As visual functions controlled, at least in part, by dopamine, absolute sensitivity, spatial contrast sensitivity, temporal (including flicker) sensitivity and colour vision are reviewed. Possible cellular and synaptic bases of the visual dysfunctions observed during retinal degenerations are discussed in relation to dopaminergic control. It is concluded that impairment of the dopamine system during retinal degenerations could give rise to many of the visual abnormalities observed. In particular, the involvement of dopamine in controlling the coupling of horizontal and amacrine cell lateral systems appears to be central to the visual defects seen.

Aging↗