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PubMed1991

Topography and morphology of retinal ganglion cells in Falconiforms: a study on predatory and carrion-eating birds.

The topographic distribution of retinal ganglion cells and their cell body size have been studied in five Falconiform species, including predatory (chilean eagle Buteo fuscenses australis, and sparrow hawk Falco sparverius) and carrion-eating (chimango caracara Milvago chimango; condor Vultur gryphus, and black vulture Coragyps atratus) birds. All these species had a well defined nasal fovea and a horizontal streak. Instead of a temporal fovea as in eagles and hawks, an afoveate temporal area is present in chimango, condor, and vulture. The highest ganglion cell density was found in the nasal fovea of Falco and Buteo with 65,000 and 62,000 cells/mm2, respectively. A negative correlation between ganglion cell density and cell body size was found in all the species studied. The specializations of the temporal retina showed a rather homogenous population of medium sized neurons, while the nasal foveas showed a homogeneous population of smaller ganglion cells. Finally, the peripheral retina showed a heterogeneous population of large, medium, and small ganglion cells. Predatory behavior appears to be closely related to foveal specializations, and is best exemplified in the eagle and hawk and to a lesser extent in the chimango.

Animals↗

PubMed1997

Pax-6, Prox 1, and Chx10 homeobox gene expression correlates with phenotypic fate of retinal precursor cells.

PURPOSE: To study the expression patterns of the homeobox genes Pax-6, Prox 1, and Chx10 during chick retinal development in vivo and in vitro. METHODS: Sections of paraformaldehyde-fixed, paraffin-embedded eyes were obtained at a range of developmental stages. In situ hybridization was carried out on tissue sections using digoxigenin-labeled sense and antisense RNA probes that recognize chicken Pax-6 and Prox 1 (whose sequences were already available), and chicken Chx10 (which was cloned and sequenced as part of this study). Selected developmental stages were also studied by immunocytochemistry with antibodies against Pax-6 and Prox 1, and by Northern blot analysis using 32P-labeled probes. RESULTS: Until embryonic day (ED) 5, in situ hybridization shows widespread, diffuse distribution of all three genes. Between ED 6 and ED 8, however, they acquire distinct, topographically specific patterns of expression. The Prox 1 signal is predominantly expressed in the prospective horizontal cell layer of the neuroepithelium, decreases vitreally, and is absent from ganglion cells and the prospective photoreceptor layer. Pax-6 is strongly expressed only in the prospective ganglion-cell and amacrine-cell regions at the same stages, and is not detected in prospective photoreceptors. Chx10 expression becomes concentrated in the future bipolar-cell region of the inner nuclear layer. Similar patterns are maintained by ED 15 through ED 18, after cell differentiation has taken place. Pax-6 and Prox 1 immunoreactive materials showed nuclear localization and a pattern of laminar distribution equivalent to that seen by in situ hybridization. CONCLUSIONS: These results suggest that the differentiated fate of retinal precursor cells may be influenced by Pax-6, Prox 1, or Chx10, this hypothesis is now being tested using dissociated chick embryo retinal cell cultures.

Amino Acid Sequence↗

PubMed1990

[Retinal ganglion cell topography during prenatal development].

A fundamental feature of the human visual system is nonuniform distribution of ganglion cells across the retinal surface. In adults, the density of ganglion cells peaks around the fovea and declines sharply towards the periphery, whereas in fetal retina it does not. In the fetal retina, the retinotopic map is dominated by nonuniform expansion and/or ganglion cell death. We examined how the numbers and distributions change according to the horizontal eccentricity from the foveola, using toluidine blue stained vertical sections of the human fetal retina (gestational age 32W and 40W). The vertical section of the fovea showed almost similar density at 32 weeks, 40 weeks and in adults. This fact suggested that the fundamental structure of the fovea is already established at 32W. In the nasal retina, the cellular density was higher than that in the temporal half at 32W, then markedly decreased at 40W and in adults. We assume that in the nasal retina, it is impossible to account for the cell decrease only with nonuniform expansion and that even after 32W ganglion cell death occurs. On the other hand, in the mid-temporal retina, the cellular density was almost similar at 32W, 40W and in adults. It suggested that in the mid-temporal retina, the topography is already established at 32W. In the peripheral temporal retina, the cellular density was relatively high at 32W and decreased at 40W and in adults. In this area, the topography is still changing. We assume that in the fetal retina, retinotopic map is dominated by several factors and the dominant factor differs according to stage and retinal area.

Cell Count↗

PubMed2003

Role of protein kinase C family in the cerebellum-dependent adaptive learning of horizontal optokinetic response eye movements in mice.

Among the subtypes of the Ca2+-dependent protein kinase C (PKC), which play a crucial role in long-term depression (LTD), both alpha and gamma are expressed in the cerebellar floccular Purkinje cells. To reveal the functional differences of PKC subtypes, we examined the adaptability of ocular reflexes of PKCgamma mutant mice, which show mild ataxia and normal LTD. In mutant mice, gains of the horizontal optokinetic eye response (HOKR) were reduced. Adaptation of the HOKR was not affected but its retinal slip dependency was altered in mutant mice. Sustained 1-h sinusoidal screen oscillation, which induced a relatively large amount of retinal slips in both mutant and wild-type mice, increased the HOKR gain in wild-type mice but not in mutant mice. In contrast, exposure to 1 h of sustained slower screen oscillations, which induced relatively small retinal slips in mutant and wild-type mice, increased the HOKR gain in both mutant and wild-type mice. Adaptation of the HOKR of the mutant mice to slow screen oscillation and those of wild-type mice to fast and slow screen oscillations were all abolished by local applications of a PKC inhibitor (chelerythrine) within the flocculi. Electrophysiological and anatomical studies showed no appreciable changes in the sources and magnitudes of climbing fibre inputs, which mediate retinal slip signals to the flocculus in the mutant mice. These results suggest that PKCgamma has a modulatory role in determining retinal slip dependency, and other PKC subtypes, e.g. PKCalpha, may play a crucial role in the adaptation of the HOKR.

Adaptation, Physiological↗

PubMedDate not supplied

Similar effects of carbachol and dopamine on neurons in the distal retina of the tiger salamander.

Though there is considerable evidence that dopamine is an important retinal neuromodulator that mediates many of the changes in the properties of retinal neurons that are normally seen during light adaptation, the mechanism by which dopamine release is controlled remains poorly understood. In this paper, we present evidence which indicates that dopamine release in the retina of the tiger salamander, Ambystoma tigrinum, is driven excitatorily by a cholinergic input. We compared the effects of applying carbachol to those of dopamine application on the responses of rods, horizontal cells, and bipolar cells recorded intracellularly from the isolated, perfused retina of the tiger salamander. Micromolar concentrations of dopamine reduced the amplitudes of rod responses throughout the rods' operating range. The ratio of amplitudes of the cone-driven to rod-driven components of the responses of both horizontal and bipolar cells was increased by activation of both D1 and D2 dopamine receptors. Dopamine acted to uncouple horizontal cells and also off-center bipolar cells, the mechanism in the case of horizontal cells depending only upon activation of D1 receptors. Carbachol, a specific cholinomimetic, applied in five- to ten-fold higher concentrations, produced effects that were essentially identical to those of dopamine. These effects of carbachol were blocked by application of specific dopamine blockers, however, indicating that they are mediated secondarily by dopamine. We propose that the dopamine-releasing amacrine cells in the salamander are under the control of cells, probably amacrine cells, which secrete acetylcholine as their transmitter.

Ambystoma↗

PubMed1990

A light- and electron-microscopic investigation of the optic tectum of the frog, Rana pipiens, I: The retinal axons.

There are several different groups of ganglion cells in the retina of the frog. Although their axons are thought to terminate in different layers of the optic tectum, little is known about the morphology of their terminal arbors or their synaptic targets. The present paper reports the results of a layer-by-layer study of horseradish peroxidase labeled retinal axons in the optic tectum of Rana pipiens. Light and electron microscopy was used to study the axon's laminar distribution, patterns of arborization, and synaptic contacts. Labeled retinal axons were found in all of the superficial layers of the tectum (A-G). From layer to layer, the retinal axons differed markedly in the diameter of their parent axons (0.2-3.0 microns) and in the morphology and horizontal extent of their terminal arbors. Five classes of synaptic terminals could be distinguished in the tectum. The retinal terminals belonged to a class characterized by round, medium-sized synaptic vesicles. They made synaptic contact with dendrites and other axon terminals in each of the layers. They were always the presynaptic component. The postsynaptic dendrites were often the vertically oriented processes of cells located in the deeper layers. The postsynaptic terminals belonged to a class distinguished by their flat, medium-sized vesicles. These terminals in turn contacted what appeared to be dendrites. In layer eight, the retinal axons were often large, spoon-shaped boutons that ended in apposition with the somata of the layer.

Animals↗

PubMed1981

Spatio-temporal cross-correlation analysis of catfish retinal neurons.

1. The receptive field properties of visual neurons in the retina of the catfish are studied by a white noise spatio-temporal stimulus. The spatial and temporal inputs of the stimulus are independent and lead to complete linear characterizations and local nonlinear characterizations of the neural response. 2. Horizontal cells, bipolar cells, and sustained or Type N amacrine cells all yield spatially coherent linear correlations. The horizontal cells have the shortest latency by these methods and exhibit a late depolarizing component that is wider in spatial extent than the initial hyperpolarizing component. Depolarizing Type N neurons have center-hyperpolarizing local nonlinearity. 3. Transient or Type C amacrine cells do not correlate well with the intensity of the stimulus, even though the Fast variety responds vigorously to the stimulus. 4. Ganglion cells are classified into Excitatory, Inhibitory and biphasic classes based upon their linear correlations. Some ganglions exhibit responses dependent upon the orientation of stimulus. Although linear correlation of the Excitatory class is similar to that of the depolarizing Type N cell, the locally nonlinear character of these cell types is distinct. The receptive field of the inhibitory ganglion cells has strong locally excitatory nonlinearity.

Animals↗

PubMed1999

Immunocytochemical localization of cannabinoid CB1 receptor and fatty acid amide hydrolase in rat retina.

Cannabinoids have major effects on central nervous system function. Recent studies indicate that cannabinoid effects on the visual system have a retinal component. Immunocytochemical methods were used to localize cannabinoid CB1 receptor immunoreactivity (CB1R-IR) and an endocannabinoid (anandamide and 2-arachidonylglycerol) degradative enzyme, fatty acid amide hydrolase (FAAH)-IR, in the rat retina. Double labeling with neuron-specific markers permitted identification of cells that were labeled with CB1R-IR and FAAH-IR. CB1R-IR was observed in all cells that were protein kinase C-immunoreactive (rod bipolar cells and a subtype of GABA-amacrine cell) as well as horizontal cells (identified by calbindin-IR). There was also punctate CB1R-IR in the distal one-third of the inner plexiform layer (IPL) that could not be assigned to a cell type. FAAH-IR was most prominent in large ganglion cells, whose dendrites projected to a narrow band in the proximal IPL. Weaker FAAH-IR was observed in the soma of horizontal cells (identified by calbindin-IR); the soma of large, but not small, dopamine amacrine cells (identified by tyrosine hydroxylase-IR); and dendrites of orthotopic- and displaced-starburst amacrine cells (identified by choline acetyltransferase-IR) but in less than 50% of the starburst amacrine cell somata. The extensive distribution of CB1R-IR on horizontal cells and rod bipolar cells indicates a role of endocannabinoids in scotopic vision, whereas the more widespread distribution of FAAH-IR indicates a complex control of endocannabinoid release and degradation in the retina.

Amidohydrolases↗

PubMed1996

Morphologic and neurochemical target selectivity of regenerating adult photoreceptors in vitro.

Regenerating adult central nervous system (CNS) neurons must re-establish synaptic circuits in an environment very different from that present during development. However, the complexity of CNS circuitry has made it extremely difficult to assess the selectivity and mechanisms of synaptic regeneration at the cellular level in vivo. The synaptic preferences of adult photoreceptors were examined by using a defined cell culture system known to support regenerative process growth, presynaptic varicosity formation, and establishment of functional synapses. Immunolabeling for synaptic vesicle protein 2 and ultrastructural analysis demonstrated that cell-cell contacts made by photoreceptors were synaptic in nature. Target selectivity was determined by quantitative analysis of contacts onto normal and novel target cell types in cultures in which opportunities to contact all retinal cell types were present. Target cells were identified by morphology and immunolabeling for the amino acid neurotransmitters glutamate, aspartate, gamma-aminobutyric acid (GABA), and glycine. Regenerating photoreceptors showed a strong preference for novel multipolar cell targets (amacrine and ganglion cells) over normal photoreceptor, horizontal, and bipolar cell targets. Additionally, photoreceptors were selective for targets containing the transmitter GABA. These results indicate first, that the normal synaptic partners for photoreceptors are not intrinsically the optimal targets for regenerative synapse formation, and second, that GABA may modulate synaptic targeting by adult photoreceptors.

Ambystoma↗

PubMed2006

AII amacrine cells in the distal inner nuclear layer of the mouse retina.

We serendipitously found a distal Disabled-1 (Dab1)-immunoreactive cell in retina of the C57BL/6J black mouse. The somata of these cells are located in the outermost part of the inner nuclear layer (INL). Their processes extend toward the outer plexiform layer (OPL), receiving synaptic inputs from horizontal and interplexiform cells. In the current study, we name this cell the "distal Dab1-immunoreactive cell." Double-labeling experiments demonstrate that the distal Dab1-immunoreactive cell is not a horizontal cell. Rather, the distal Dab1 cell appears to be a misplaced AII cell, by being glycine transporter-1-immunoreactive and by resembling the latter cell in an electron microscopic analysis. A distal Dab1 cell had been reported in the FVB/N mouse retina, a model of retinitis pigmentosa (Park et al. [2004] Cell Tissue Res 315:407-412). However, here, we found this distal Dab1-immunoreactive cell in the adult and normal developing mouse retinas. Hence, we show that such cells do not require the loss of photoreceptors as suggested previously (Park et al. [2004] Cell Tissue Res 315:407-412). Instead, two other pieces of data suggest an alternative explanation sources for distal Dab1 cells. First, we find a correlation between the number of these cells in the left and right eyes Second, developmental analysis shows that the distal Dab1-immunoreactive cell is first observed shortly after birth. At the same time, AII cells emerge, extending their neurites into the inner retina. These data suggest that distal Dab1-immunoreactive cells are misplaced AII amacrine cells, resulting from genetically modulated anomalies owing to migration errors.

Amacrine Cells↗

PubMed1992

Calcium binding protein (calbindin D28k) immunoreactivity in the hamster superior colliculus: ultrastructure and lack of co-localization with GABA.

The expression of specific calcium binding proteins is being used increasingly as a potential neuroanatomical marker for neurons with similar functions. In this study, the distribution of calbindin D28k in the superior colliculus (SC) of adult hamsters was examined by light and electron microscopy. Calbindin immunoreactivity was prominent in specific regions and laminae of the SC throughout its rostrocaudal extent, and was found to label horizontal, vertical and stellate cell types. In addition, calbindin label highlighted "bridges" of neuronal processes in the intermediate layers. The most frequent calbindin-immunoreactive profiles seen in the electron microscope were dendrites, some of which were post-synaptic to apparent retinal ganglion cell axon terminals. Labelled axons and axon terminals were less frequently encountered. There was considerable overlap between the size distribution of calbindin D28k-immunoreactive neurons and that of GABA-immunoreactive or Nissl stained neurons in the SC. However, using a double fluorescent labelling technique, and examination of the tissue with confocal laser microscopy, no neurons were observed in the hamster SC that showed immunoreactivity for both calbindin and GABA. In this regard, the SC is similar to the mammalian lateral geniculate nucleus and the pretectum, but differs from the neocortex, where calbindin and GABA are colocalized. The demonstration in the SC, as well as other parts of the nervous system, of sub-populations of neurons that contain distinct calcium-binding proteins suggests that these neurons have different functional properties. Correlative studies may clarify the relevance of these cytoplasmic components as cell markers, as well as their different patterns of association with neurotransmitters and peptides.

Animals↗

PubMed1987

High-pass resolution targets in peripheral vision.

Visual acuity was measured at 10 degree intervals on the horizontal meridian in two normal subjects, using high-pass spatial frequency filtered test targets in a computer graphics display. The close similarity between detection and recognition thresholds resulted in quick and reliable measurements. Peripheral acuity was proportional to local retinal ganglion cell separation. High-pass targets appear to be nearly ideal for clinical perimetry because of the easy test task and the possibility of interpreting results in terms of numbers of functional neuroretinal channels. The major limitation appears to be a somewhat fuzzy definition of small, circumscribed defects.

Adult↗

PubMed1999

Altered development of dopaminergic cells in the retina of weaver mice.

Postnatal degeneration of dopaminergic (DA) cells is known to occur in mesencephalic nuclei of mutant weaver mice, whereas retinal DA content is reported to be unchanged in the adult animal. To determine whether morphological changes occur in the weaver retinal DA system, we compared weaver and control developing and adult retinas after tyrosine hydroxylase (TH) immunohistochemistry. The density and distribution of DA cells were analyzed using Dirichlet tessellation. Not only was no DA cell loss found in adult weaver retinas, but we even observed an increase in DA cells in weaver compared to control retinas between postnatal days 14 and 30. Furthermore, some unusual features were found during the latter period: atypical cells (representing a maximum of 12% of the whole DA cell population) were observed, and these differed from typical DA cells in terms of both location (slightly more external within the inner nuclear layer) and appearance (flat somata, round and clear nuclei, thick dendritic trunks emerging laterally and giving rise to horizontal processes). Some of the atypical cells were intermingled in a delicate network lying in a more outer focal plane than the main DA plexus. The expression of GIRK2, a G protein-related inward rectifying K(+) channel responsible for the weaver syndrome, was investigated. Although no GIRK2 labeling was demonstrated in DA cells, its possible involvement in the transient disturbances observed in the weaver DA retinal system is discussed.

Animals↗

PubMed1996

Quantitative analysis of triphasic (H3) horizontal cell-cone connectivity in the cyprinid fish (roach) retina.

Although horizontal cells encode chromatic information by means of a variety of spectrally opponent light-evoked response patterns, their synaptic connections with the different spectral classes of cone are not completely understood. In the cyprinid fish retina, where a hierarchical set of interactions between horizontal cells and cone types has been proposed, a particular type of horizontal cell generates light-evoked triphasic (red-hyperpolarizing/green depolarizing/blue-hyperpolarizing) responses. In the present study, we have studied the cone connectivity of these cells by intracellular recording and staining in the roach retina. The horizontal cells were first identified electrophysiologically using spectral stimuli, and then stained intracellularly with horseradish peroxidase. Light microscopy revealed that the cells had consistent H3-like morphologies. At an ultrastructural level, these horizontal cells were deduced to contact selectively blue-sensitive cones. Within the cone pedicles, the majority (approximately 80%) of the contacts were "central" to synaptic ribbons. Some 50% of the "lateral" processes were large and engulfed cone cytoplasm. Spinules were present within the contacted pedicles but not upon the dendrites of the stained horizontal cells, although previous work had suggested that horseradish peroxidase would not interfere with spinule dynamics. The results are discussed in terms of existing modes of horizontal cell-cone connectivity in cyprinid fish retinae.

Animals↗

PubMedDate not supplied

AMPA-selective glutamate receptor subunits GluR2 and GluR4 in the cat retina: an immunocytochemical study.

AMPA-selective glutamate receptors play a major role in glutamatergic neurotransmission in the retina and are expressed in a variety of neuronal subpopulations. In the present study, immunocytochemical techniques were used to visualize the distribution of GluR2 and GluR4 subunits in the cat retina. Results were compared with previous localizations of GluR1 and GluR2/3. Staining for GluR2 was limited to a small number of amacrine and ganglion cells whereas GluR4 staining was present in A-type horizontal cells, many amacrine cells including type AII amacrine cells, and the majority of the cells in the ganglion cell layer. Analysis of synaptic relationships in the outer plexiform layer showed the GluR4 subunit to be concentrated at the contacts of cone photoreceptors with A-horizontal cells. In the inner plexiform layer, both GluR2 and GluR4 were postsynaptic to cone bipolar cells at dyad contacts although GluR2 staining was limited to one of the postsynaptic elements whereas GluR4 immunoreactivity was often seen in both postsynaptic elements. Unlike GluR2, GluR4 was also postsynaptic to rod bipolar cells where it could be visualized in processes of AII amacrine cells. The data indicate that GluR3 and GluR4 subunits are colocalized in a number of cell types including A-type horizontal cells, AII amacrine cells, and alpha ganglion cells, but whether they are combined in the same multimeric receptors remains to be determined.

Animals↗

PubMed1975

Retinal mechanisms of visual adaptation in the skate.

Electrical potentials were recorded from different levels within the skate retina. Comparing the adaptive properties of the various responses revealed that the isolated receptor potential and the S-potential always exhibited similar changes in sensitivity, and that the b-wave and ganglion-cell thresholds acted in concert. However, the two sets of responses behaved differently under certain conditions. For example, a dimly iluminated background that had no measurable effect on the senitivities of either of the distal responses, raised significantly the thresholds of both the b-wave and the ganglion cell responses. In addition, the rate of recovery during the early, "neural" phase of dark adaptation was significantly faster for the receptor and S-potentials than for the b-wave or ganglion cell discharge. These results indicate that there is an adaptive ("network") mechanism in the retina which can influence significantly b-wave and gaglion cell activity and which behaves independently of the receptors and horizontal cells. We conclude that visual adaptation in the skate retina is regulated by a combination of receptoral and network mechanisms.

Animals↗

PubMed1984

Cell populations of the ganglion cell layer: displaced amacrine and matching amacrine cells in the pigeon retina.

The proportion and size distribution of ganglion and non-ganglion cells in the ganglion cell layer of different areas of the pigeon retina was examined in whole-mounts of the retina by retrograde axonal transport of horseradish peroxidase (HRP) from large brain injections. A maximum of 98% of cells were labelled in the red field and a maximum of 77% in the peripheral yellow field. Unlabelled cell bodies were 30% smaller than labelled ganglion cells and had a mean diameter of 6.2 microns and a size range of 4 to 9 microns. The morphology of cells in the ganglion cell layer was examined by Golgi staining of retinal whole-mounts. Small glia, displaced amacrine and ganglion cells were found. Displaced amacrine cell bodies were about 30% smaller than ganglion cells and their size distribution was similar to the unlabelled cells in HRP preparations. Displaced amacrine cells had small rounded cell bodies (mean diameter 6.2 microns) increasing in size with eccentricity, and a unistratified dendritic tree of fine, nearly radial, varicose dendrites in sublamina 4 of the inner plexiform layer. They had elliptical dendritic fields (mean diameter 66 micron) aligned parallel to the retina's horizontal meridian. A population of amacrine cells was found with somas at the inner margin of the inner nuclear layer and soma and dendritic morphology matching those of displaced amacrines. These amacrine cells had unistratified dendritic trees at the junction of sublaminae 1 and 2 of the inner plexiform layer. Pigeon displaced amacrine cells and their matching amacrines are similar to starburst cells of the rabbit retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Protein gene product 9.5-immunoreactive retinal neurons in normal developing rats and rats with optic nerve or tract lesion.

The present immunocytochemical study indicates that protein gene product 9.5 (PGP 9.5) in the rat retina first appears in a population of neurons in the inner and central part of the neuroblast layer at embryonic day (E) 14. Presumptive horizontal cells which are PGP 9.5 positive were observed at E17. At birth, cells in the inner nuclear layer and ganglion cell layer (GCL) as well as the inner plexiform layer (IPL) were positive. Further differentiation, particularly the appearance and the formation of immunoreactive sublaminae in the IPL, was observed in the first 2 postnatal weeks. This pattern reached adult levels by postnatal day 14. In rats with unilateral neonatal optic tract lesion or optic nerve transection as young adults, 43-45% of the immunoreactive cells were lost in the GCL. However, only minor changes were detected in the IPL, suggesting that amacrine cells contribute mainly to the PGP 9.5 immunoreactivity in this laminar zone of the retina.

Aging↗