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Results for “Retinal Horizontal Cells”

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PubMed1999

Retinal projections and retinal ganglion cell distribution patterns in a sturgeon (Acipenser transmontanus), a non-teleost actinopterygian fish.

Retinal projections in a sturgeon were studied by injecting biocytin or HRP into the optic nerve. The target areas are the preoptic area, thalamus, area pretectalis, nucleus of posterior commissure, optic tectum, and nuclei of the accessory optic tract. Furthermore, a few labeled fibers and terminals were found in a ventrolateral area of the caudal telencephalon. All retinal projections are bilateral, although contralateral projections were more heavily labeled. Retrogradely labeled neurons were found in the ventral thalamus bilaterally. Retinal projections in sturgeons are similar to those of other non-teleost actinopterygians and chondrichthyans (sharks), in terms of the targets and extent of bilateral projections. Distribution patterns of ganglion cells in the retina were examined in Nissl-stained retinal whole mount preparations. The highest density areas were found in the temporal and nasal retinas, and a dense band of ganglion cells was observed along the horizontal axis between the nasal and temporal areas of highest density. The density of ganglion cells in the dorsal retina is the lowest. The total number of ganglion cells was estimated to be about 5 x 10(4) in a retina. The existence of a low density area in the dorsal retina suggests reduced visual acuity in the ventral visual field.

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PubMed1995

Retinal neurones specific for centrifugal modulation of vision.

The avian retina receives centrifugal projections from a midbrain nucleus, the isthmo-optic nucleus. We labelled target cells for the isthmo-optic fibres by intracellular injections of Lucifer Yellow in fixed retinal slices. The isthmo-optic recipient (IOR) cells had no major dendrites extending into the inner plexiform layer, but had a thin axon-like process running horizontally in the junction between the inner nuclear layer and the inner plexiform layer. The IOR cells were morphologically similar to the association amacrine cells of Cajal. Immunohistochemical localization of aspartate and glutamate in the IOR cells suggested that they may use these excitatory amino acids as neurotransmitters.

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PubMed1985

Sequential treatment with low doses of kainic acid alters sensitivity of retinal cell types.

Examination of chick retinae soon after treatment with a single intraocular injection of 5 nmol kainic acid revealed degenerative changes in a small population of neurons located in the outer aspect of the inner nuclear layer, consistent with either bipolar and/or horizontal cells. Damage to the outer plexiform layer was also present. After one week, affected retinae were clear of neuronal debris. Following a second, identical injection, one week after the first, there was degeneration of a different population of neurons confined to the inner aspect of the inner nuclear layer indicative of amacrine cells. As amacrine cells were the only cell type affected by the second injection, our results suggest that they are directly affected by the second dose of kainic acid. The pattern of neuronal damage following successive doses of kainic acid appears to be potentially useful technique in elucidating retinal circuitry.

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PubMed1997

Ultrastructural and biochemical studies on the neuroprotective effects of excitatory amino acid antagonists in the ischemic rat retina.

The effects of glutamate receptor agonists were evaluated, by utilizing the electron microscope, in a photothrombotic occlusion model of rat retinal vessels in order to study the ischemic damage and its antagonism in each morphologically identified population of retinal neurons. Rats were systemically injected with rose bengal fluorescein dye and one of their eyes was then exposed to bright light. This treatment caused neuronal damage and reduced the activities of the neuronal marker enzymes, choline acetyltransferase and glutamate decarboxylase, by approximately 75%. A single intravitreal injection of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzoquinoxaline (NBQX, 10-50 nmol), an antagonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors, or of thiokynurenate (100-400 nmol), which also antagonizes N-methyl-D-aspartate (NMDA) receptors, performed immediately after the lesion, significantly reduced this loss. The electron microscope examination showed major damage in each type of retinal neuron, the pigment epithelium, and the microvessels. NBQX or thiokynurenic acid reduced, in a comparable manner, the effects of ischemia on the pigment epithelium, the photoreceptors, and the bipolar and the horizontal cells. NBQX was particularly efficient in reducing the damage to the amacrine cells located in the inner nuclear layer. The displaced amacrine and ganglion cells were not protected by NBQX but were almost completely spared in animals treated with thiokynurenate. These results show that antagonism of AMPA receptors is sufficient to reduce ischemic damage in a large number of retinal neurons, but that neuroprotection in the ganglion cell layer may be obtained only with agents which also antagonize NMDA receptors.

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PubMed1999

Clonal expansion and cell dispersion in the developing mouse retina.

The present study has used two different approaches for labelling progenitor cells at the optic vesicle stage in order to examine patterns of clonal expansion and cellular dispersion within the developing retina. X-inactivation transgenic mice and chimeric mice expressing the lacZ reporter transgene were examined during development and in adulthood to study the radial and tangential dispersion of proliferating neuroepithelial cells and postmitotic retinal cells of known identities. Chimeric retinas were used to measure tangential dispersion distances, while transgenic retinas were used to assess the frequency of tangential dispersion for individual populations of retinal neurons. Tangential dispersion is shown to be a universal feature of particular retinal cell types, being contrasted with the strictly radial dispersion of other cells. Tangential dispersion is a relatively short-distance phenomenon, with distinct dispersion distances characteristic for cone, horizontal, amacrine and ganglion cells. Embryonic and postnatal retinas show that tangential dispersion occurs at different times for these distinct cell types, associated with their times of differentiation rather than their neurogenetic periods. These developmental results rule out the possibility that tangential dispersion is due to a passive displacement produced by the proliferation of later-born cells, or to the lateral dispersion of a dividing sibling; rather, they are consistent with the hypothesis that tangential dispersion plays a role in the establishment of the orderly spatial distribution of retinal mosaics.

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PubMed1980

Different regional specializations of neurons in the ganglion cell layer and inner plexiform layer of the California horned shark, Heterodontus francisci.

We have described a population of neurons in the retinal of a shark, Heterodontus francisci, which is precisely aligned within the inner plexiform layer (IPL) and which differs from neurons in the ganglion cell layer (GCL) in soma size and topographical distribution. GCL neurons are relatively small and form a horizontally oriented visual streak; IPL neurons are significantly larger and form a circular specialization in the far temporal retina. Thus, it appears that there are two distinct retinal specializations in Heterodontus: one subserving frontal vision and one which provides a panoramic view of the lateral visual field.

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PubMed1998

Iron-induced cytotoxicity in cultured rat retinal neurons.

Oxidative stress has been proposed as a major injury mechanism in the central nervous system including the retina. In this study, as an initial attempt to study the mechanism of oxidative injury in the retina, we developed a cell culture model by utilizing the iron exposure paradigm. Exposure of rat retinal cultures for 24 hours to 10-40 MicroM ferrous or ferric chloride induced a concentration-dependent death of retinal neurons but not of photoreceptors or astrocytes. An antioxidant, trolox effectively attenuated the iron-induced death of neurons and photoreceptors in a dose-dependent manner whereas neither glutamate receptor antagonists nor cycloheximide were protective. Of retinal interneurons, GABAergic neurons were more vulnerable to the iron toxicity than calbindin (+) horizontal neurons. These findings show that iron exposure induces anti-oxidant-sensitive neuronal injury in retinal culture, independent of the excitotoxic or the apoptotic mechanisms. Of retinal neurons, different cell types exhibit differential vulnerabilities to the iron-induced oxidative injury. This simplified culture model system may be useful in elucidating mechanisms of oxidative injury in the retina.

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PubMed1984

A neurofibrillar method stains solitary (primary) cilia in the mammalian retina: their distribution and age-related changes.

Richardson's reduced silver method, developed for the staining of autonomic nerve fibres in the mammalian intestine, is shown consistently to stain solitary (primary) cilia and diplosomes of the cells of the retinae of cats and rabbits. The cilia comprise a centriole, a basal body and an axoneme with a 9 + 0 complement of microtubules. Probably all retinal cells possess a cilium during their development but, contrary to previous reports, not all retain the axoneme after birth. Axonemes are absent from horizontal, bipolar, microglia, Müllerian, and probably some other glial, cells; all of which showed paired centrioles (diplosomes) after staining. Photoreceptor, amacrine, interplexiform, displaced amacrine and ganglion cells have each one cilium. These differences between cell types persist, without significant change, in the retina of adult rabbits up to the age of 2 years, and in the cat up to 5 years. The alpha-type ganglion cells of the cat are an exception. In 4 to 8-week-old kittens they are all ciliated, like other types of ganglion cells. But by two years about 30% of central area alpha-cells lack an axoneme. Individual cells may have only diplosomes, unusual dispositions of the centrioles in the perikaryal cytoplasm, or even show complete loss of the whole ciliary apparatus. By 5 years of age the proportion of those alpha-cells showing unusual arrangements has increased to approximately 70%, while less than 5% of the other types of ganglion cells are so affected. Cilia of peripheral alpha-cells change at a different rate and by 5 years of age are approximately like the 2-year-old central area population.

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PubMed2001

Differential expression of GAD(65) and GAD(67) during the development of the rat retina.

The development of synthetic enzymes in the GABAergic system (GAD(67) and GAD(65)) of the rat retina was analyzed from birth to the 4th postnatal week by the reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemistry. As previously observed for GABA, immunoreactive GAD(67) profiles are seen clearly in the inner retinal layers at birth. At the end of the 1st week of postnatal life, immunolabeling is detected in amacrine and/or ganglion cells and in horizontal cells. GAD(67) immunoreactivity is transiently expressed in horizontal cells and disappears during the 3rd postnatal week. GAD(65) however does not develop until the 5th postnatal day. Immunolabeling is detected in the processes layering the inner plexiform layer (IPL) before being detected in the amacrine and/or ganglion cell bodies. The appearance of transcripts for GAD coincided with the appearance of the proteins. A transient form of mRNA transcripts of the GAD(67) gene containing an extra exon (ES-exon) is also observed which disappears progressively from birth to the 4th postnatal week. This form synthesizes a truncated, enzymatically inactive protein, which could participate in the regulation of GABA synthesis from glutamate present at high levels during retinogenesis.

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PubMed2004

Terminal nerve and vision.

The vertebrate retina receives efferent input from different parts of the central nervous system. Efferent fibers are thought to influence retinal information processing but their functional role is not well understood. One of the best-described retinopetal fiber systems in teleost retinae belongs to the terminal nerve complex. Gonadotropin-releasing hormone (GnRH) and molluscan cardioexcitatory tetrapeptide (FMRFamide)-containing fibers from the ganglion of the terminal nerve form a dense fiber plexus in the retina at the border of the inner nuclear and inner plexiform layer. Peptide-containing fibers surround and contact perikarya of dopaminergic interplexiform cells in teleost retina. In vitro experiments demonstrated that exogenously supplied GnRH mediates dopaminergic effects on the membrane potential and on the morphology of dendritic tips (spinules) of cone horizontal cells. These effects can be specifically blocked by GnRH-antagonists, indicating that the release of dopamine and dopamine-dependent effects on light adaptation of retinal neurons are affected by the terminal nerve complex. Recent data have shown that olfactory information has an impact on retinal physiology, but its precise role is not clear. The efferent fiber of the terminal nerve complex is one of the first retinopetal fiber systems for which the sources of the fibers, their cellular targets, and several physiological, morphological, and behavioral effects are known. The terminal nerve complex is therefore a model system for the analysis of local information processing which is influenced by a distinct fiber projection.

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PubMed1986

Horizontal cell signal is smaller with texture-like nonuniform patterns than with uniform fields of the same space-average illuminance.

While measurement of the pertinent response as a function of flash intensity has been a standard procedure in vision research, we ask here what happens to horizontal cells in the vertebrate retina if the flash energy is varied through the density of a large number of small light spots rather than through the intensity of uniform illumination. The experiment described here demonstrates that the electrical response of horizontal cells in the turtle retina is consistently smaller with the present dot-density modulation than with the usual intensity modulation, even though the comparison is made when the mean irradiance per photoreceptor is equal in the two methods of modulation. Thus, the spatial summation, an important retinal function often thought to provide a base signal level for contrast detection, is affected significantly by how the visual pattern is structured at a level of microscopic dimension far smaller than the receptive field. The present finding, which seems to be a new form of area-intensity effect, can be explained if the dendritic membrane conductance of horizontal cells at each synaptic site increases at a progressively higher rate with decreases of the corresponding local illuminance. This possibility is discussed in the light of relevant photoreceptor response data, the presumed sigmoidal trend of the postsynaptic chemosensitivity and a simple electrical analog of contiguous horizontal cells.

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PubMed1984

The visual field representation of the rat ventral lateral geniculate nucleus.

The representation of the visual field in the ventral lateral geniculate nucleus (LGNv) was studied in rats anesthetized with urethane by recording the response of single units to visual stimulation. Receptive fields of LGNv units were plotted on a campimeter, 60 cm in diameter, which was placed 30 cm from the contralateral eye. LGNv neurons responded mainly to stimulation of the contralateral eye with on-tonic characteristics. Few neurons responded only to stimulation of the ipsilateral eye and no binocular interaction was observed. Retinotopic organization was clearly seen in the LGNv; the nasal visual fields were represented dorsally, the temporal fields ventrally, and the upper to lower visual fields were in the rostrolateral to caudomedial parts of the LGNv. A given point in the visual field is represented along a line running through the LGNv in a rostrocaudal direction. Almost the entire horizontal extent of the contralateral visual field was represented in the LGNv, whereas vertically the visual field between 40 degrees above and 20 degrees below the distribution axis was represented. The major axis of the strip of the visual field containing all the RF centers, which is referred to as the distribution axis, inclined nasally up and temporally down at an angle of 10.4 degrees to the 0 degree horizontal meridian line. The representation of the distribution axis in the retina was in accordance with the major axis of retinal ganglion cell distribution (Fukuda, '77; Schober and Gruschka, '77).

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PubMed1997

Somatostatin-like immunoreactive cells in the ground squirrel retina.

Immunocytochemical techniques were employed to locate somatostatin (SS)-containing cells in the retina of the 13-lined ground squirrel (Spermophilus tridecemlineatus). In normal retinas immunostain was limited to neuronal processes, yet distinctly labeled somata were detected in retinas of animals pretreated with colchicine. Labeled cell bodies were located in the outermost and innermost portions of the inner nuclear layer (INL) and in the ganglion cell layer (GCL). The largest population of SS-like immunoreactive neurons was found in the innermost INL. These cells were identified as small and medium sized amacrine cells whose soma diameters ranged from 4 to 14 microns. A smaller population of immunoreactive cells was observed in the outermost region of the INL. These cells, presumptive horizontal cells, were found mainly in peripheral regions of the retina. Immunoreactive cells in the GCL were of two types: displaced amacrines, and retinal ganglion cells. SS-positive axons in the optic fiber layer suggest that some of the immunoreactive GCL neurons were ganglion cells, and it is our opinion that these cells belong to a class of associational ganglion cells previously identified in other species.

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PubMed1980

Electrophysiological analysis of taurine and glycine action on neurons of the midpuppy retina. I. Intracellular recording.

Intracellular recordings were carried out in the prefused retine-eyecup preparation of the mudpuppy. Taurine and glycine were added to the bathing medium to study their effects on different retinal neurons. In a few cases, gamma-aminobutyric acid was exogenously applied to compare GABA vs taurine/glycine action. Receptors and horizontal cells were relatively insensitive to taurine/glycine, while amacrines and ganglion cells were comparatively more sensitive to these agents. Bipolar cells proved to be differentially effected by inhibitory amino acids: hyperpolarizing (OFF) bipolars were depressed by taurine/glycine and proved less sensitive to GABA; depolarizing (ON) bipolars were suppressed by GABA and were comparatively less sensitive to glycine/taurine. Taurine and glycine had identical actions on neurons and both were about equally effective at the same concentration. Strychnine blocked the action of taurine and glycine. The patterns of glycine/taurine sensitivity and their effects on second order neurons eliminate taurine as a photoreceptor transmitter; one or both of these agents may be utilized by a subclass of amacrine cells which interact with hyperpolarizing bipolars, other amacrine cells and ganglion cells. It appears that taurine or glycine or both may be selectively involved in OFF channel activity, while GABA may subserve an equivalent role for the ON channel.

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PubMedDate not supplied

GABA and GABA(A) receptor antagonists alter developing cone photoreceptor development in neonatal rabbit retina.

Gamma aminobutyric acid (GABA) has been established as an important developmental signal in a number of regions of the central nervous system (CNS), including retina. Our previous studies have shown that GABAergic horizontal cells act as the initial synaptic target for developing cone photoreceptors in neonatal rabbit retina. Since intraocular injections of the GABA(A) receptor antagonists, picrotoxin or bicuculline, disrupt cone synaptogenesis in vivo, GABA released from horizontal cells may provide a necessary signal for cone axon growth and/or synapse formation. In the current report, we have used cultured retinal explants to examine the effects of GABA(A) receptor antagonists on other aspects of developing cones. These include the distribution pattern of cone cell bodies across the outer surface of the retina and the expression of GABA(A) receptors within both cone cell bodies and axonal processes. Peanut agglutinin (PNA), a plant lectin that specifically labels cone plasma membrane and extracellular matrix, was used to monitor cone development, and a GABA(A) receptor antibody against the beta2/3 subunits of the protein was used to label GABA(A) receptors. Results showed that cones maintained in the explant culture express GABA(A) receptors in a temporal and spatial pattern similar to that observed in vivo, namely a low expression of receptors on cone cell bodies at postnatal day 1 (P1), peaking around P3 and diminishing by P7. Neonatal retinal explants exposed to the GABA(A) receptor antagonists, bicuculline (10 microM) or SR95531 (5 microM), for 24 h in culture showed disruption of the normal distribution of cone cell bodies. When GABA (100 microM) was added along with either antagonist, cone cell bodies appeared normal. Neither bicuculline nor SR95531 alone had any effect on the general morphology of other retinal layers, suggesting that these GABA(A) receptor antagonists at the concentrations used were not acting as nonspecific disruption agents. The effects of GABA antagonists were confined to the first week after birth with no disruption seen in P9 or adult explant cultures. These data provide a direct demonstration of the necessity for GABAergic input to cones during active synaptogenesis. As we have previously shown, GABA(A) receptor activation causes a substantial increase in intracellular calcium concentrations in cones and thereby could provide a mechanism by which GABA regulates cone maturation.

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PubMed1997

[The selective suppression of GABA on cone-driven horizontal cells in carp retina].

Intracellular recordings were made from horizontal cells in the superfused, isolated carp retina and effects of GABA on rod- and cone-driven horizontal cells were studied. Bath-applied GABA (0.5-5 mmol/L) resulted in a hyperpolarization of dark membrane potential and a suppression of light responses of L-type cone horizontal cells. In 7 out of 10 cells tested the effects of GABA were completely blocked by bicuculline, an antagonist of GABAA receptors. In the presence of 0.5 mmol/L Co2+, 2 mmol/L GABA could not induce any change in dark membrane potential in 8 out of 12 cells, but cause slight depolarization in other 4 cells. These results suggest that the GABA effects may be mediated by GABAA receptors on cone terminals in the majority of the L-type cone horizontal cells. GABA had no effect on rod horizontal cells.

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PubMed2004

The distribution of c-myb immunoreactivities in the adult mouse retina.

The myb gene family is composed of three different myb-related genes, A-, B- and c-myb. Among these, the presence of c-myb mRNA in developing and adult retina was previously reported. However, further study on the expression of c-myb in the retina is warranted because the previous study was only performed on developing retinal tissues by in situ hybridization technique. Therefore, in this study, we tried to perform immunohistochemical study, with a focus on the c-myb protein expression in adult retina. Although the cell types were unconfirmed, c-myb protein was likely to have been found in the ganglion, amacrine, horizontal and photoreceptor cells, judging from their locations and morphologies. The experimental data suggested that c-myb immunoreactivities were expressed by the cells in the neural retina, even in the adult stage, especially within some types of cells in specified retinal layers. This suggests that c-myb might play a role in the physiology of the retinal cells, not only in differentiation during retinal development.

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PubMed1985

Distributions of aspartate aminotransferase and malate dehydrogenase activities in rat retinal layers.

Aspartate aminotransferase (AAT), an enzyme interconverting glutamate and aspartate, has been suggested to be a marker for glutamatergic and/or aspartatergic neurons. However, AAT, glutamate, and aspartate are also involved in cellular metabolism, e.g., the malate-aspartate shuttle. To investigate the extent to which AAT might be involved in these several functions in retina, the distribution of AAT activity in rat retinal layers was compared to that of malate dehydrogenase (MDH), an enzyme of aerobic metabolism proposed to be physically complexed with AAT in the malate-aspartate shuttle mechanism. The distribution of AAT activity in retinal layers closely paralleled that of MDH (correlation coefficient AAT versus MDH = 0.93). AAT activity was proportionately higher than MDH in the photoreceptor inner segments, containing a high density of mitochondria, and in the outer plexiform layer (OPL), containing photoreceptor terminals and bipolar and horizontal cell processes. The amount of total AAT activity in the inner segments related to the mitochondrial isoenzyme is almost twice that in the other layers tested, including the OPL. The correlation between AAT and MDH activities is consistent with AAT involvement in retinal energy metabolism, although other functions, such as neurotransmission, are possible.

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