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Results for “Retinal Horizontal Cells”

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PubMed1991

Effects of light stimuli on the release of dopamine from interplexiform cells in the white perch retina.

Interplexiform cells are centrifugal neurons in the retina carrying information from the inner to the outer plexiform layers. In teleost fish, interplexiform cells appear to release dopamine in the outer plexiform layer after prolonged darkness that modulates the receptive-field size and light responsiveness of horizontal cells (Mangel & Dowling, 1985; Yang et al., 1988a, b). It has been proposed that interplexiform cells may also release dopamine upon steady illumination because horizontal cells' receptive fields shrink in the light (Shigematsu & Yamada, 1988). Here, we report the shrinkage of the receptive fields of horizontal cells seen in the presence of background illumination is not blocked by dopamine antagonists, indicating that dopamine does not underlie the receptive-field size changes observed during steady illumination. Flickering light, however, does appear to stimulate the release of dopamine from the interplexiform cells, resulting in a marked reduction of horizontal cell receptive-field size. Taken together, experiments on horizontal cells indicate that dopamine is released from interplexiform cells in the teleost retina after prolonged darkness and during flickering light, but that dopamine release from interplexiform cells during steady retinal illumination is minimal.

Animals↗

PubMedDate not supplied

Propagating waves in visual cortex: a large-scale model of turtle visual cortex.

This article describes a large-scale model of turtle visual cortex that simulates the propagating waves of activity seen in real turtle cortex. The cortex model contains 744 multicompartment models of pyramidal cells, stellate cells, and horizontal cells. Input is provided by an array of 201 geniculate neurons modeled as single compartments with spike-generating mechanisms and axons modeled as delay lines. Diffuse retinal flashes or presentation of spots of light to the retina are simulated by activating groups of geniculate neurons. The model is limited in that it does not have a retina to provide realistic input to the geniculate, and the cortex and does not incorporate all of the biophysical details of real cortical neurons. However, the model does reproduce the fundamental features of planar propagating waves. Activation of geniculate neurons produces a wave of activity that originates at the rostrolateral pole of the cortex at the point where a high density of geniculate afferents enter the cortex. Waves propagate across the cortex with velocities of 4 microm/ms to 70 microm/ms and occasionally reflect from the caudolateral border of the cortex.

Algorithms↗

PubMed2006

OPA1 expression in the human retina and optic nerve.

Mutations in the optic atrophy type 1 (OPA1) gene give rise to human autosomal dominant optic atrophy. The purpose of this study is to investigate OPA1 protein expression in the human retina and optic nerve. A rabbit polyclonal antiserum was generated using a fusion protein covering amino acids 647 to 808 of the human OPA1 protein as the immunogenic antigen. Western blot and immunofluorescence staining were performed to examine OPA1 expression in the human retina and optic nerve. In human retina, we found that OPA1 expression was clearly present in retinal ganglion cells and photoreceptors. OPA1 immunoreactivity was also present in the nerve fiber layer, inner plexiform layer and outer plexiform layer. However, OPA1 protein was not detected in the choline acetyltransferase-positive, calretinin-positive, and calbindin-positive amacrine cells, nor in the calbindin-positive horizontal cells. In the human optic nerve, expression of OPA1 was present in the axonal tract that was labeled with neurofilament specific antibody. In conclusion, expression of OPA1 gene is present in the mitochondria-rich regions of the retina and optic nerve. This suggests that OPA1 protein might be involved in the functioning of the mitochondria that are present in both inner and outer retinal neurons.

Adult↗

PubMed2000

Visual system in a diurnal marsupial, the numbat (Myrmecobius fasciatus): retinal organization, visual acuity and visual fields.

The visual system of the numbat (Myrmecobius fasciatus), a highly endangered diurnal marsupial, has been investigated both anatomically and behaviorally. The ganglion cell layer, examined in cresyl-violet stained wholemounts, contained 832,800 ganglion cells; the number of ganglion cells corresponded to optic axon counts. An area centralis was located in the mid-temporal retina, where cells formed a bilayer, but there was no evidence of a visual streak. Visual acuity, estimated from counts of peak ganglion cell density (8,100/mm(2)) and measurements of posterior nodal distance (7.84 mm), was found to be 6.3 cycles per degree. The value was similar to that of 5.2 cycles per degree estimated by behavioral tests. Sectioned material revealed the presence of numerous oil-droplets in a cone-dominated retina. A rich retinal vasculature of the end-artery type of paired arteries and veins formed beds in the ganglion cell and inner nuclear layers. Measurements of visual fields revealed a binocular overlap of 80 degrees in the horizontal plane, and a total field of view approaching 240 degrees of visual angle. Monitoring of pupillary responses with an infrared video camera showed that the numbat possesses a remarkably wide, static pupil. Our results are discussed in relation to the ecology of the species and its phylogeny.

Animals↗

PubMed2001

The development and mature organisation of the end-artery retinal vasculature in a marsupial, the dunnart Sminthopsis crassicaudata.

The end-artery retinal vasculature of a marsupial, the fat-tailed dunnart, was defined by India ink injection and studied in wholemounts. In the adult, the vitreal vasculature supplying the ganglion-cell layer has major paired-vessels in a horizontal H shape. These vessels skirt the area centralis and visual streak that are supplied by fine end-loops. A second vascular layer of uniformly distributed endloops arises from the superficial vessels and lies at the inner nuclear/outer plexiform border. During development, vessels enter the eye via the optic nerve head to form the upper vasculature, assuming an essentially mature arrangement prior to the formation of the area centralis and visual streak. Vessels then descend to form the lower bed. Unlike the cat, the dunnart has retinal vessels that are patent throughout development, their growth is interstitial and reductive remodelling is not seen. A retinal end-artery system may have evolved in marsupials because their precocity requires a vasculature that is functional from early stages of development.

Animals↗

PubMed1988

Retinal ganglion cell topography in teleosts: a comparison between Nissl-stained material and retrograde labelling from the optic nerve.

The retinal topography of cells within the ganglion cell layer of three teleost species is examined in Nissl-stained material in which all neuronal elements containing Nissl substance in the cytoplasm are counted. A topographic comparison is made with retrogradely labelled ganglion cells to differentiate the proportion of nonganglion cells not possessing an axon joining the optic nerve. In the three species studied 92%, 80%, and 66% were found to be the maximum proportion of true ganglion cells in the area centralis, horizontal streak, and periphery, respectively. The proportion of nonganglion cells in the total population of cells counted was 24%. The major contribution to this discrepancy is from peripheral nonspecialized regions of the retina. There is little difference in both topography and peak densities of retinal ganglion cells between the two techniques. The soma areas of both populations are analysed, with the homogeneous nonganglion cell population possessing cells between 5 and 15 micron2 and the heterogeneous ganglion cell soma between 5 and 68 micron2, increasing in size with eccentricity.

Animals↗

PubMed1981

Synapse formation and modification between distal retinal neurons in larval and juvenile Xenopus.

A serial section analysis of photoreceptor synaptic bases was undertaken in the clawed frog Xenopus laevis. The developmental period from tadpole stage 48 through metamorphosis was studied. Horizontal cells contacted rod and cone photoreceptors at ribbon synapses; the number of such contacts per receptor base was constant for rods, but increased for cones as a function of developmental stage. In pre-metamorphic animals bipolar cells contacted receptors only through basal junctions; their number in cone bases increased dramatically during development but was unchanged in rod bases. A densitometric estimation of the cleft width of basal junctions showed that it ranged from 10 to 18 nm, but the junctions could not be divided reliably into the 'wide' and 'narrow' categories reported for other vertebrate species. Near metamorphic climax a new type of ribbon-related bipolar cell junction appeared. Gap junctions between horizontal cells and conventional synapses of horizontal cell onto bipolar cell processes were first seen in mid-larval developmental stages.

Animals↗

PubMed1988

Immunocytochemical localization of gamma-aminobutyric acid (GABA) in the cat superior colliculus.

This paper reports the pattern of labeling in the cat superior colliculus produced by an antiserum raised against BSA-conjugated gamma aminobutyric acid (GABA) and visualized by light and electron microscope immunocytochemistry. Neuropil labeling was densest within the zonal and superficial gray layers but was also found in the deep layers. Neurons labeled by the GABA antibody were also most dense within the zonal and superficial gray layers, although many labeled neurons were also found in the deeper layers. The ratio of labeled to unlabeled cells varied from an average of 45% in the superficial subdivision and the intermediate gray layer to less than 30% in the deeper laminae. Almost all intensely labeled cells were small (mean area = 127 micron 2) and had varied morphologies. Several types of labeled cell were observed with the electron microscope. One type had a horizontal, fusiform cell body and a deeply invaginated nucleus. Another type had a small round or ovoid cell body with cytoplasm clumped at one end. Labeled cells with other morphologies were also occasionally seen. No labeled glial cells were found. Two types of vesicle-containing dendrite were stained by the GABA antibody. One type had loose accumulations of small synaptic vesicles and often received input from retinal terminals. Another type had spines also containing small synaptic vesicles. Labeled dendrites without synaptic vesicles were also seen frequently. Putative axon terminals labeled by the GABA antibody had densely packed synaptic vesicles and formed symmetric synaptic contacts. Labeled myelinated axons were also commonly found. These results confirm those using uptake of tritiated GABA (Mize et al.: J. Comp. Neurol. 202:385-396, '81, J. Comp. Neurol, 206:180-192, '82) in that two of the same classes of GABA neuron, horizontal I and granule I cells, were identified in the superficial laminae. However, the GABA antiserum used in this study also revealed a third class of GABA neuron with vesicle-containing spines. The antiserum also labeled a significant number of putative GABAergic neurons located in the deep subdivision of the cat superior colliculus which were not previously recognized by using transmitter autoradiography.

Animals↗

PubMed2000

Modifications of retinal neurons in a mouse model of retinitis pigmentosa.

Animal models of retinitis pigmentosa include the rd mouse, in which a mutation of a rod-specific phosphodiesterase leads to the rapid loss of photoreceptors during the early postnatal life. Very little is known about changes occurring in inner retinal neurons after photoreceptor loss. These changes are important in view of the possibility of restoring vision in retinas with photoreceptor degeneration by means of cell transplantation or direct stimulation of inner layers. In this paper, we show that bipolar and horizontal cells of the rd mouse retina undergo dramatic morphological modifications accompanying photoreceptor loss, demonstrating a dependence of second order neurons on these cells. While describing modifications of the rd retina, we also provide quantitative information about neurons of the wild-type mouse retina, useful for future studies on genetically altered animals.

Animals↗

PubMed2005

Photopic vision in eels: evidences of color discrimination.

Several classes of second-order retinal neurons have been studied electrophysiologically in European eel (Anguilla anguilla) from two different localities, Lake Seliger in Russia and the coastal waters of the Adriatic Sea in Montenegro. The majority of L-horizontal cells (68 explored) had both rod and cone inputs, an uncommon phenomenon among teleosts. Pronounced color-opponent properties, often taken as pointing to the capacity of color vision, were identified in one amacrine cell, apparently of the "blue/yellow" (or "blue/green") type. Microspectrophotometric measurements revealed two different spectral classes of cones with absorption maxima at about 525 and 434 nm. The existence of green-sensitive and blue-sensitive cone units was thus revealed by both electrophysiological and microspectrophotometric techniques.

Adaptation, Ocular↗

PubMed1995

The visual system of the Florida garfish, Lepisosteus platyrhincus (Ginglymodi). IV. Bilateral projections and the binocular visual field.

Infusion of cobaltous-lysine into the optic nerve of juvenile Florida garfish reveals that the preoptic area, pretectum, thalamus and the mediorostral and ventrolateral poles of the optic tectum each receive bilateral, monosynaptic input. The bilateral input to the mediorostral pole of the tectum projects via the dorsal optic tract and terminates in the rostral half of the tectum. The bilateral input to the ventrolateral tectum projects via the ventral optic tract and extends the whole length of the tectum. The incidence of direct ipsilateral input to the tectum suggests binocular vision may play a functional role in the survival of this species. In order to test this hypothesis, we examined the retinal distribution of ipsilateral retinal ganglion cells that project to the mediorostral tectum and the size and location of the binocular visual field. Cell distribution was examined by retrograde labelling with rhodamine-conjugated dextran amine delivered by microinjections into the mediorostral pole of the right optic tectum. In the ipsilateral retina, ganglion cells are distributed in a narrow temporoventral area with a mean of 0.44 +/- 0.14 x 10(3) cells per mm2 apposing the retinal margin. In the contralateral retina, ganglion cells are also distributed within this temporoventral region with a mean peak density of 2.33 +/- 0.47 x 10(3) cells per mm2. Three broad classes of ipsilaterally projecting retinal ganglion cells (orthotopic cells within the ganglion cell layer, displaced cells within the inner nuclear layer, and giant cells within the ganglion and inner nuclear layers) are identified, intermingled in both the ipsilateral and contralateral retinae after retrograde labelling from the mediorostral pole of the tectum. Ophthalmoscopic mapping of the monocular and binocular visual fields reveals two small frontal wedges of binocular overlap. A dorsal wedge (12 degrees wide) extends from approximately 7 degrees above the horizontal axis to 10 degrees beyond the vertical axis, and a ventral wedge (20 degrees wide) extends approximately 10 degrees below the horizontal axis to 15 degrees beyond the vertical axis. The dorsal binocular visual field is subtended by the temporoventral region of the retina possessing both ipsilaterally and contralaterally projecting ganglion cells which terminate in the mediorostral pole of the optic tectum. Therefore, the partial decussation of retinal ganglion cell axons at the optic chiasm brings information from corresponding regions of the binocular visual field into register in the mediorostral pole of the optic tectum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Retinal ganglion cell death during optic nerve regeneration in the frog Hyla moorei.

In the frog Hyla moorei we have estimated there to be between approximately 450,000 and 750,000 cells in the retinal ganglion cell layer. Optic axon counts and retrograde transport of horseradish peroxidase (HRP) indicated that 72-76% of these were ganglion cells. Cells of this type were distributed as a temporally situated area centralis within a horizontal visual streak. Cell and optic axon counts showed that there was an approximately 40% loss of ganglion cells during optic nerve regeneration. Ganglion cells appeared chromatolysed by 6-8 days after an extracranial nerve crush but there was no indication of cell death until 15 days. By this stage anterograde transport of HRP indicated that axons had reached the chiasma. Death was first seen in the area centralis, extended along the streak, and finally was observed in the periphery by 65 days; cell counts demonstrated that at this time the wave of death was almost complete. We have previously shown by electrophysiological visual mapping (Humphrey and Beazley, '82) and confirmed in this study that visuotectal projections were retinotopically organized during regeneration. Multiunit receptive fields were initially large but progressively refined starting in nasal field (temporal retina) to restore a normal projection. The similar sequences whereby the visuotectal projection became refined and death took place in the retinal ganglion cell layer suggested that death may be related to a process of organization within the regenerating projection. In normal animals primary visual pathways revealed by anterograde transport of HRP were essentially similar to those of Rana pipiens and R. esculenta. Regenerating axons generally remained within optic pathways. Exceptions were a retinoretinal projection which was not completely withdrawn even after 1,028 days and a direct projection to the ipsilateral tectum via an inappropriate part of the optic tract.

Animals↗

PubMed2003

Neuronal integration in an abutting-retinas culture system.

PURPOSE: Limited integration is consistently observed between subretinal transplants and host retinas. In the current study, an in vitro model system for studying connections forming between two abutting retinas was developed. METHODS: Neuroretinas were dissected from normal wild-type (WT) mice and green fluorescent protein (GFP) transgenic mice (obtained at postnatal days [P]0, P5, or P60), as well as from adult rd mice. Pieces from two different retinas (WT-WT, GFP-WT, GFP-rd) were placed side-by-side (contacting each other at the margins) or overlapping each other in organ cultures for 7 or 12 days. The abutting retinal pieces derived from animals of the same age (P5-P5; P60-P60) or of different ages (P0-P60; P5-P60). Retinal cells and fibers were visualized in wholemount preparations and in cross sections by immunocytochemistry using antibodies against neurofilament (NF+), neuronal nitric oxide synthase (NOS+), and protein kinase C (PKC+) and by GFP fluorescence (GFP+). RESULTS: In side-by-side pairs (WT-WT, GFP-WT), numerous horizontal cell fibers (NF+) and amacrine cell fibers (NOS+) crossed the interface between the two pieces, forming continuous plexiform layers. In overlapping pairs, NF+, NOS+, and PKC+ fibers displayed parallel plexiform layers, and no crossover of fibers was observed in any of the pair combinations examined (WT-WT, GFP-WT, GFP-rd). Some integration was seen only in small areas where the structure of both retinal pieces was disrupted at the interface. CONCLUSIONS: The results demonstrate the ability of neurites to extend between abutting retinas and to make appropriate target choices when they are placed side-by-side. However, this ability is limited when they overlap each other, similar to that observed in subretinal transplantation.

Animals↗

PubMed1995

Distribution of GAD-like immunoreactivity in the retina and central visual system of Rana pipiens.

Immunohistochemistry was used to survey the distribution of glutamic acid decarboxylase (GAD), the synthesizing enzyme for gamma-aminobutyric acid (GABA), throughout the visual system of the frog Rana pipiens. GAD-like immunoreactivity (GAD-LI) was assessed in the retina, in primary retinorecipient targets, and in thalamic nuclear groups postsynaptic to primary retinal terminal zones. Within the retina, the inner plexiform layer displayed intense GAD-LI, but immunoreactivity was absent in the ganglion cell layer (GCL). Putative amacrine, bipolar, and horizontal cell somata were also labeled. Centrally, GAD-LI was observed in all primary visual nuclei. Dense, GAD-like immunoreactive punctate structures (puncta), presumably terminals, were observed in the pretectal nucleus lentiformis mesencephali, posterior thalamic neuropil, and uncinate neuropil. GAD-like immunoreactive puncta were noted in several laminae of the optic tectum, with the highest concentrations located within the 9th and 8th laminae. Moderate numbers of GAD-like immunoreactive puncta were found in the mesencephalic nucleus of the basal optic root, and two thalamic neuropils--corpus geniculatum and neuropil of Bellonci. The ventrolateral area, posterocentral nucleus, and posterolateral nucleus all contained sparse amounts of GAD-LI. These observations suggest that GABA plays an important physiological role in all central visual areas of Rana pipiens.

Animals↗

PubMed1998

The modulation of intercellular coupling in the retina.

Gap-junction coupling between retinal neurons of the same (homologous) or different (heterologous) type can be modulated dynamically by neurotransmitters and by the level of ambient illumination. The homologous coupling of both horizontal cells and rod (AII) amacrine cells is reduced by dopamine, but there appear to be cell and species differences in how the ambient illumination interacts with the dopaminergic system to modulate the coupling. Both the homologous coupling of horizontal cells and the heterologous coupling between AII amacrine cells and cone bipolar cells are reduced by nitric oxide, but it is not known if changes in illumination modulate coupling through an endogenous nitrergic mechanism. The heterologous coupling between rod and cone photoreceptors is modulated by illumination, but the endogenous mechanism has not been identified.

Animals↗

PubMed2001

Structure and function of photoreceptor and second-order cell mosaics in the retina of Xenopus.

The structure, physiology, synaptology, and neurochemistry of photoreceptors and second-order (horizontal and bipolar) cells of Xenopus laevis retina is reviewed. Rods represent 53% of the photoreceptors; the majority (97%) are green light-sensitive. Cones belong to large long-wavelength-sensitive (86%), large short-wavelength-sensitive (10%), and miniature ultraviolet wavelength-sensitive (4%) groups. Photoreceptors release glutamate tonically in darkness, hyperpolarize upon light stimulation and their transmitter release decreases. Photoreceptors form ribbon synapses with second-order cells where postsynaptic elements are organized into triads. Their overall adaptational status is regulated by ambient light conditions and set by the extracellular dopamine concentration. The activity of photoreceptors is under circadian control and is independent of the central body clock. Bipolar cell density is about 6000 cells/mm2 They receive mixed inputs from rods and cones. Some bipolar cell types violate the rule of ON-OFF segregation, giving off terminal branches in both sublayers of the inner plexiform layer. The majority of them contain glutamate, a small fraction is GABA-positive and accumulates serotonin. Luminosity-type horizontal cells are more frequent (approximately 1,000 cells/mm2) than chromaticity cells (approximately 450 cells/mm2). The dendritic field size of the latter type was threefold bigger than that of the former. Luminosity cells contact all photoreceptor types, whereas chromatic cells receive their inputs from the short-wavelength-sensitive cones and rods. Luminosity cells are involved in generating depolarizing responses in chromatic horizontal cells by red light stimulation which form multiple synapses with blue-light-sensitive cones. Calculations indicate that convergence ratios in Xenopus are similar to those in central retinal regions of mammals, predicting comparable spatial resolution.

Animals↗

PubMed1982

Neural correlates of optokinetic nystagmus in the mesencephalon of Rana pipiens: a functional analysis.

The effects of lesions of the anuran mesencephalic retinal terminal fields on horizontal optokinetic nystagmus (OKN) were examined. Lesion sites which produced effects upon OKN responses were as follows: BOR, nBOR, peri-nBOR, the large-celled pretectal nucleus, and the dorsal tegmental gray and deep tectal layers. Transection of BOR generally resulted in an increase in saccadic frequently at the lower stimulus velocities. Lesions of nBOR produced a decrease in the frequency of both head and eye saccades in the middle to high range of stimulus velocities. The only lesions which totally abolished horizontal OKN were those located medical to nBOR, in the peri-nBOR region. Lesions of the large-celled pretectal nucleus and dorsal tegmental gray substantially reduced both head and eye saccades at all stimulus velocities. Small lesions in the deep tectal layers also depressed OKN frequency. These studies indicate that horizontal OKN may be mediated by a number of structures within the anuran mesencephalon.

Animals↗

PubMed1991

Morphology, density and distribution of tyrosine hydroxylase immunoreactive cells in the retina in the gerbil Meriones shawi. Relationships with horizontal cells.

Dopamine neurons have been demonstrated with the use of tyrosine hydroxylase (TH)-immunohistochemistry in the retina of Meriones shawi, a wild species of pigmented sand rat, in order to compare their morphology, density, and distribution with those in albino laboratory rat. The morphology and density of TH-immunoreactive cells were quite comparable in the two species: the dopamine cell population was composed of amacrine cells, displaced amacrine cells, and interplexiform cells, these latter being more numerous in the albino rat. The distribution of dopamine cells was more homogeneous in the sand rat retina where a peak density in the area centralis was not observed. The relationships between TH-immunoreactive cells and horizontal cells, demonstrated by their immunoreactivity to calbindin, have been observed in view of the dopamine action driven by scleral processes of interplexiform cells. A close vicinity occurred between 40% of the TH-immunoreactive cell and horizontal cell somata within the inner nuclear layer.

Animals↗