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PubMed1986

Identification and characterization of cell types in monolayer cultures of rat retina using monoclonal antibodies.

This study describes the identification and differentiation of neonatal rat retinal cells in monolayer cultures. A panel of monoclonal antibodies was used as a molecular probe of both cell type and developmental stage. Previously described cell-type specific monoclonal antibodies were used to label rod photoreceptors, horizontal cells, amacrine cells or ganglion cells. Two new antibodies that react with rat retina are described. The first, RET-G7, reacts with a cytoplasmic antigen of Muller glia, astrocytes and some horizontal cells. The second, RET-B2, reacts with bipolar cells and photoreceptor inner segments. Two main findings are presented. The first is that each of the major subclasses of retinal neurons have been unambiguously identified in these cultures. The morphology of some subclasses was very characteristic. All photoreceptors, as defined by reactivity with antibody RET-P1, were small spherical cells with one or fewer processes. Horizontal cells, as defined by reactivity with antibody B-1, were large with a characteristic multipolar network of processes. Bipolar and amacrine cells, on the other hand, were of similar size and could only be distinguished on the basis of immunocytochemical labeling. The second finding is that while RET-B2 antigen appeared on bipolar and photoreceptor cells after about 5 days in culture, several Muller cell and photoreceptor antigens were not expressed in monolayer cultures. The results suggest that the expression of some molecules in culture is the result of properties intrinsic to the cells whereas expression of others depends upon extrinsic factors or cell interactions that may not be present in monolayer cultures.

Animals↗

PubMed2000

Retinal ganglion cells projecting to the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic system in macaque monkeys.

Using classical neuroanatomical retrograde tracing methods we investigated the retinal ganglion cells projecting to the nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system (NOT-DTN) in macaque monkeys. Our main aim was to quantify the strength of the projection from the ipsilateral retina to the NOT-DTN. We therefore examined the number, distribution, and soma size of retinal ganglion cells involved in this projection. Electrophysiologically controlled small injections into the NOT-DTN revealed a clearly bilateral retinal projection originating mainly from the central retina but also involving peripheral retinal regions. Labelled cells were found nasally in the contralateral retina and temporally in the ipsilateral retina with some overlap in the fovea. The projection from the ipsilateral retina was 36-43% of that from the contralateral retina. On average, only 1-6% of the local population of ganglion cells projected to the NOT-DTN. Small soma size and large dendritic fields imply that in monkey rarely encountered, 'specialized' ganglion cells provide the direct retinal input to the accessory optic system (AOS). These results are discussed with respect to the symmetry of monocular horizontal optokinetic nystagmus (OKN) in primates.

Animals↗

PubMed1998

Amino acid signatures in the detached cat retina.

PURPOSE: Expressions of certain macromolecules are altered by experimental retinal detachment in the cat. Related alterations in micromolecular signatures of neurons, Müller cells, and the retinal pigment epithelium (RPE) were investigated. METHODS: High-performance immunochemical mapping, image registration, and quantitative pattern recognition were combined to analyze the amino acid contents of virtually all retinal cell types after 3 to 84 days of detachment. RESULTS: Retinal micromolecular signatures showed a spectrum of alterations. The glutamate contents of Müller cells increased and remained elevated for weeks after detachment. Multispectral signatures of Müller cells showed massive metabolic instability in early detachment stages that ultimately resolved as a homogeneous profile significantly depleted in glutamine. Retinal pigment epithelial cell signals also changed dramatically, displaying an initial glutamate spike and then a prolonged decline, even as taurine levels followed an opposite pattern of initial loss and slow restoration. Neurotransmitter signatures of surviving neurons showed extensive precursor-level variation, and, in one case, GABAergic horizontal cells displayed anomalous sprouting. CONCLUSIONS: Dramatic changes in Müller cell amino acid signatures triggered by retinal detachment are partially consistent with losses in glutamine synthetase activity. Taurine signal variations suggest that orthotopic RPE cells attempt to regulate abnormal taurine concentrations in the enlarged subretinal space. Surviving neurons possess characteristic neurotransmitter signals, but their metabolite regulation seems abnormal. On balance, microchemical and structural anomalies develop in the detached cat retina that represent serious barriers to recovery of normal visual function.

Amino Acids↗

PubMed1994

Positional disparity sensitivity of neurons in the cat accessory optic system.

There is considerable evidence supporting the view that the accessory optic system (AOS) and the closely associated nucleus of the optic tract (NOT) provide visual signals used in the control of optokinetic nystagmus (OKN). In frontal-eyed animals such as the cat and primate, the high degree of overlap in the visual fields of each eye, along with a substantial projection from the visual cortex, gives rise to an increased incidence of binocularly responsive neurons in the AOS. In previous studies, my collaborators and I have shown that visual cortical input to the AOS mediates ipsilateral eye responses and high speed tuning, and can function independently of the contralateral eye. However, beyond fairly gross assessments such as these, the binocular interactions of AOS cells have not been subject to detailed examination. The present study set out to determine whether the responses of binocular cells in the dorsal terminal nucleus (DTN) of the AOS are sensitive to horizontal retinal disparity. Single units were recorded from the DTN of anaesthetized, paralysed cats. A large random-dot pattern was moved under computer control at a constant velocity in the preferred and non-preferred direction. Convergent and divergent disparities were generated by deviating the visual axis of the contralateral (dominant) eye using wedge prisms. The responses of DTN units fell into three categories: (1) cells showing tuned excitatory responses (29% or 7 cells) consisting of a marked facilitation for a single or a limited range of disparities; (2) cells broadly tuned for inhibition (25% or 6 cells); and (3) cells relatively insensitive to disparity (46% or 11 cells), showing a relatively flat response profile across the entire range of disparity conditions, or cells without clear tuning. In summary, this study demonstrates that some AOS cells are sensitive to positional disparity and, therefore, this system may provide signals which specify the plane of motion for ocular stabilization. Some of these results have been presented in brief form [Grasse (1991a) Society of Neuroscience Abstracts, 17, 1380].

Animals↗

PubMed1996

Clinicopathologic correlation of submacular membranectomy with retention of good vision in a patient with age-related macular degeneration.

We present the clinicopathologic features of the eye of a patient with age-related macular degeneration who underwent submacular membranectomy and had retention of good visual acuity for almost 4 years despite recurrent choroidal neovascularization treated with krypton laser photocoagulation and mild expansion of the laser lesion with time. Histopathologic study of the surgically removed membrane from the right eye disclosed a thin fibrovascular membrane lined by retinal pigment epithelium on one surface. Microscopic examination of the right eye obtained post mortem disclosed a 2.75-mm (horizontal) x 2.1-mm (vertical) retinal pigment epithelium defect with overlying photoreceptor cell atrophy centered on the temporal parafoveal area, and a 0.6 x 0.1-mm subretinal pigment epithelium fibrovascular membrane with an area of retinal pigment epithelial hyperplasia and vascularization from the retina 0.4 mm temporal to the fovea. Basal laminar deposit was present in the region of the fovea and nasal parafoveal area.

Aged↗

PubMed1992

Cytoarchitecture and visual field representation in area 17 of the tammar wallaby (Macropus eugenii).

Tritiated proline was injected into one eye in the tammar wallaby and transported label was studied in the cortex after transneuronal passage through the lateral geniculate nucleus. The autoradiographic label and cytoarchitecture were used to anatomically demarcate the borders of area 17. Electrophysiological recordings from single units were done to obtain a retinotopic map of area 17. Single units in area 17 were found to have orientation sensitivity comparable to those seen in placental mammals such as cat and monkey. They could also be classified as simple, complex, and hypercomplex cells. Changes in the cortical areal magnification factor with eccentricity were found to match the drop off in retinal ganglion cell density only along the vertical meridian representation. Along the horizontal meridian, the cortical magnification falls off significantly with eccentricity, whereas the ganglion cell density shows only a mild reduction. Thus central vision, especially the binocular segment, is heavily represented at the cost of the periphery.

Animals↗

PubMed1983

Autoradiographic analysis of 3H-glutamate, 3H-dopamine, and 3H-GABA accumulation in rabbit retina after kainic acid treatment.

We have previously reported that exposure of isolated rabbit retina to 10(-3) M kainic acid produces profound morphological changes in specific retinal neurons (Hampton et al, 1981). We noted specific swelling of horizontal cell bodies and neurites, necrosis of cell bodies in the amacrine and ganglion cell layers, and swelling of elements in the inner plexiform layer. We now report a differential sensitivity to kainic acid of specific subclasses of amacrine cells autoradiographically labeled with 3H-glutamate, 3H-GABA, or 3H-dopamine. Three different effects were observed: (1) Labeling of neurons after incubation in 3H-glutamate was uniformly reduced while labeling of glia was much less affected. (2) The accumulation of 3H-dopamine was also decreased by kainic acid in two of the three labeled bands of the inner plexiform layer. The outermost labeled band was insensitive to kainic acid at the highest concentration tested (10(-2) M). These findings provide a basis for the subclassification of dopaminergic amacrine cells into at least two subclasses based on their sensitivity to kainic acid. (3) Kainic acid caused a dramatic increase in the labeling of GABAergic amacrine cell bodies and their terminals. This increased intensity may reflect a compensatory increase in uptake activity in response to kainic acid-induced depletion of endogenous GABA stores. These results confirm the highly toxic nature of kainic acid and demonstrate a high degree of specificity and complexity in its action in the retina.

Animals↗

PubMed1981

Retinal projection to the nucleus of the optic tract in the cat as revealed by retrograde transport of horseradish peroxidase.

Retrograde transport of horseradish peroxidase injected iontophoretically into the nucleus of the optic tract of cats revealed that the direction-selective cells in this pretectal nucleus receive direct retinal projections from small retinal ganglion cells, the so-called gamma-cells. These cells from a horizontal band on the contralateral retina. Few labeled cells are found in the ipsilateral temporal retina. The input from the contralateral retina is 10 times more numerous than from the ipsilateral one. In both retinae the highest concentration of labeled cells is near the area centralis.

Animals↗

PubMedDate not supplied

A neural model of foveal light adaptation and afterimage formation.

Psychophysical research has documented the existence of three processes in light adaptation: a fast subtractive process, a divisive process that is fast at light onset and slower at light offset, and a very slow subtractive process (Hayhoe et al., 1987). In the neural model developed here, the fast subtractive process is identified with horizontal cell feedback onto cones and the divisive process with amacrine cell feedback onto bipolar cells. The very slow subtractive process is identified with the modulatory feedback circuit from amacrines via interplexiform cells to horizontal cells. A nonlinear dynamical model is developed incorporating these aspects of retinal circuitry along with both ON- and OFF-center M and P pathways. This model is shown to account for many aspects of foveal light adaptation, including negative afterimage formation, and to explain a number of the physiological differences between M and P ganglion cells, including their differing contrast-response functions.

Adaptation, Physiological↗

PubMed2000

Foveate vision in deep-sea teleosts: a comparison of primary visual and olfactory inputs.

The relative importance of vision in a foveate group of alepocephalid teleosts is examined in the context of a deep-sea habitat beyond the penetration limits of sunlight. The large eyes of Conocara spp. possess deep convexiclivate foveae lined with Müller cells comprising radial shafts of intermediate filaments and horizontal processes. Photoreceptor cell (171.8 x 10(3) rods mm(-2)) and retinal ganglion cell (11.9 x 10(3) cells mm(-2)) densities peak within the foveal clivus and the perifloveal slopes, respectively, with a centro-peripheral gradient between 3:1 (photoreceptors) and over 20:1 (ganglion cells). The marked increase in retinal sampling localized in temporal retina, coupled with a high summation ratio (13:1), suggest that foveal vision optimizes both spatial resolving power and sensitivity in the binocular frontal visual field. The elongated optic nerve head is comprised of over 500 optic papillae, which join at the embryonic fissure to form a thin nervous sheet behind the eye. The optic nerve is divided into two axonal bundles; one receiving input from the fovea (only unmyelinated axons) and the other from non-specialized retinal regions (25% of axons are myelinated), both of which appear to be separated as they reach the visual centres of the central nervous system. Comparison of the number of primary (first-order) axonal pathways for the visual (a total of 63.4 x 10(6) rod photoreceptors) and olfactory (a total of 15.24 x 10(3) olfactory nerve axons) inputs shows a marked visual bias (ratio of 41:1). Coupled with the relative size of the optic tecta (44.0 mm3) and olfactory bulbs (0.9 mm3), vision appears to play a major role in the survival of these deep-sea teleosts and emphasizes that ecological and behavioural strategies account for significant variation in sensory brain structure.

Animals↗

PubMed1980

Second and third visual areas of the cat: interindividual variability in retinotopic arrangement and cortical location.

1. The cortical location and the retinotopic arrangement of the second (V2) and third (V3) visual areas in the cat have been investigated with single and multiple unit recordings in anaesthetized and immobilized animals.2. V2 and V3 are arranged side by side anterior and medial to V1 and occupy the lateral gyrus and the postlateral sulcus. In addition, V2 spreads to postlateral parts of the lateral sulcus and, occasionally, to the posterior suprasylvian gyrus. The contralateral lower hemifield is represented on the lateral gyrus, the area centralis and the horizontal meridian are found in most animals in the anterior part of the postlateral sulcus, and the representation of the upper hemifield occupies the posterior part of the postlateral sulcus.3. The detailed retinotopic arrangement of the visual field maps shows two characteristic features. First, the retinotopy at the V2/V3 border differs between lower and upper hemifield. In the lower hemifield the periphery of the fields is represented, whereas in the upper hemifield the border between the representations is formed by a sector running along the horizontal meridian about 5-10 degrees in the upper hemifield. Thus the lower field arrangement resembles that of rodents, and the upper field arrangement is similar to that of primates. Secondly, the periphery of a part of the visual field is not continuously represented, but forms patches or islands (Donaldson & Whitteridge, 1977). The islands are bounded by visual field representations closer to the vertical meridian. The way the visual field is represented at the border between V2 and V3 introduces discontinuities into the visual field maps: adjacent parts of the visual field are not represented adjacently in these two prestriate areas.4. Cortical location and detailed retinotopic arrangement vary considerably from animal to animal, so that a representative map of V2 and V3 cannot be constructed. For example, the representation of the periphery of the horizontal meridian may be located either in the anterior portion of the postlateral sulcus or some mm more posteriorly, where the sulcus turns laterally. The representation of the area centralis in V3 is found either at the transition zone between lateral and postlateral sulcus, on the posterior suprasylvian gyrus, or in the posterior part of the postlateral sulcus.5. The entire hemifield is represented in V2 at least in some animals. In V3 the uppermost part of the vertical meridian seems not to be represented. In other animals only a restricted part of the contralateral visual field is represented in V2 or in V3. In these cases the receptive fields cover not more than 50 degrees out in the lower hemifield or on the horizontal meridian. In a few cases the periphery of the horizontal meridian and the upper hemifield are not at all represented in V3, or only in an incomplete manner.6. The magnification factors (Daniel & Whitteridge, 1961) become progressively smaller from V1 to V2 to V3. Hence cortical volume occupied decreases from V1 to V3. In V1 and in V2 the magnification is highest along the lower vertical meridian. In V2 the magnification along the horizontal meridian is the smallest, whereas in V1 the magnification decreases progressively from the lower vertical, to the horizontal and to the upper vertical meridian. The relationship between retinal ganglion cell densities and cortical magnification factors is discussed.

Animals↗

PubMed1985

Responsiveness and receptive field size of carp horizontal cells are reduced by prolonged darkness and dopamine.

In the fish retina the interplexiform cells contain dopamine and provide a centrifugal pathway from the inner plexiform layer to horizontal cells of the outer plexiform layer. Dopamine application reduced the responsiveness and receptive field size of cone horizontal cells, as did a prolonged period of complete darkness. Other results suggest that the interplexiform cells may release dopamine after a prolonged period in the dark. The interplexiform-horizontal cell system may modify the strength of the antagonistic surrounds of retinal neurons as a function of time in the dark.

Animals↗

PubMed2003

Color vision at low light intensity, dark adaptation, Purkinje shift, critical flicker frequency and the deterioration of vision at low illumination. Neurophysiology at the nanometer range of neural structure.

The discovery that color vision extends to low illumination reported in this communication eliminates the duplicity theory as an explanation of vision differing at high and low illumination. Instead, an explanation of the difference was found when analyzing synaptic interaction between retinal neurons, made possible by revealing the synaptic connections between the neurons through three-dimensional reconstruction of the outer plexiform layer and by applying information communicated by published recordings of the potential of retinal neurons. The synaptic connections revealed the existence of a large horizontal cell network and of cone networks. The networks contribute continuous information regarding average light intensity over an area of the retina. The opposite sign of the network input maintains bipolar cell threshold constant when illumination varies. When at low illumination the network potential approaches a minimum the consequent extensive increase of transmitter release at network synapses eliminates fine tuning of synaptic transmission at these synapses. This accounts for the deterioration of vision at low illumination by eliminating spatial brightness contrast enhancement and also accounts for the difference in critical flicker frequency at high and low illumination. Network interference accounts for the two phases of dark adaptation and for the Purkinje shift. The analysis revealed conditions for particularly fast synaptic transmission leading to cascade like transmission at sequences of synapses. The overall design of the neural circuits establishes conditions for fast processing of information. This is the consequence of the neurons responding with graded changes of the membrane potential and conducting potentials electrotonically. Such neurons are therefore particularly suitable for processing of information.

Animals↗

PubMed1991

Spatial and Temporal Patterns of Neurogenesis in the Chick Retina.

Chick embryo retinas were labelled in ovo by single injections of [3H]thymidine at selected times between days 2 and 12 of incubation. Embryos were later removed, at different stages of development, and the retinas processed for autoradiography of either serial sections or dissociated cell preparations. Analysis of unlabelled cells shows that neurogenesis starts, on day 2 of incubation, in a dorsotemporal area of the central retina, close to the posterior pole and to the optic nerve head. A gradient of neurogenesis spreads from this central area to the periphery, where neurogenesis ends, shortly after day 12, when the last few bipolar cells withdraw from the cell cycle. Additional dorsal-to-ventral and temporal-to-nasal gradients can be discerned in our autoradiographs. In all retinal sectors, ganglion cells start first to withdraw from the cell cycle, followed, with substantial overlapping, by amacrine, horizontal, photoreceptor plus Müller, and bipolar neuroblasts. Ganglion cells are also the first to reach the 50% level of unlabelled cells, followed this time by horizontal, photoreceptor, amacrine, Müller and bipolar cells. Finally, 100% levels of unlabelled cell populations are attained simultaneously by ganglion, horizontal and photoreceptor cells, followed by amacrine, then by Müller, and last by bipolar cells. Although all classes of neurons, in varying proportions, are being produced most of the time, our results also demonstrate that, in any given retinal area, the first cells leaving the cycle are determined to become ganglion cells, and the last ones bipolar cells, and not other types.

Journal Article↗

PubMed1980

Effects of GABA and glycine on the distal cells of the cyprinid retina.

Two putative retinal neurotransmitters, gamma-aminobutyric acid (GABA) and glycine, were applied to the isolated carp and goldfish retinas while intracellular recordings from horizontal cells and cones were made. At relatively low concentrations (0.1-1 mM), GABA consistently hyperpolarized dark-adapted H1 or L-type cone horizontal cells and cone photoreceptors, reduced light evoked responses and suppressed the on-transients. The effects of GABA on H1 horizontal cells were abolished when Co2+ was applied to the retina, indicating that GABA exerts its effects on the horizontal cells via the receptors. Thus GABA is likely to be involved in the feedback synapse between H1 horizontal cells and the cones. Low concentrations of glycine (0.1-1 mM), hyperpolarized a number of H2 or C-type horizontal cells and selectively abolished their depolarizing responses to red light; thus glycine may be involved in synaptic pathways which mediate or modulate the depolarizing responses to red flashes in C-type horizontal cells.

Animals↗

PubMed1994

Size constancy, depth constancy and vertical disparities: a further quantitative interpretation.

The size and depth constancies considered here operate only at near distances (< about 2 m) in a static stimulus situation with vergence as the only cue to distance. The innervation of the extraocular muscles, as evidenced by the corollary discharge, provides information about the vergence of the eyes and hence about the egocentric distance both for symmetrical and asymmetrical vergences. Size and depth constancies are regarded as the first and second stages of a linked two-stage process. In the lateral geniculate nuclei compensatory adjustments are separately applied to each retinal image as they are received from the two eyes. The modified ocular images, with their associated vertical and horizontal disparities, now provide synaptic inputs to binocularly activated cells in the visual cortex. Then, by a process akin to the induced effect, cortical cells with geniculate afferents with vertical disparities will have their outputs expressed in terms of horizontal disparities. The horizontal disparity outputs of these cortical cells are then further multiplied by the outputs from cortical cells with geniculate afferents with horizontal disparities. It is this second multiplicative process that brings about the quadratic relationship between horizontal retinal disparity and egocentric distance. The proposed mechanisms involve the known ability of the visual system to detect and respond to vertical as well as horizontal disparities and provide a definite role for the induced effect in the perceptual process. The above neural model is based on fairly simple equations that give a remarkably adequate description of the operation of the two constancies.

Cybernetics↗

PubMed1994

A proximal retinal component in the primate photopic ERG a-wave.

PURPOSE: The monkey photopic ERG was studied during administration of glutamate analogs to determine whether the photopic a-wave derives exclusively from photoreceptors. METHODS: Monkey photopic ERGs were elicited using 200-msec flashes or 30-microseconds xenon photostrobe flashes on a steady light-adapting background of 40 cd/m2 (3.3 log scotopic troland). Intravitreal injections of APB, PDA, or both were given to block transmission to depolarizing and hyperpolarizing second-order retinal neurons, respectively. RESULTS: After injecting PDA to block light responses of horizontal cells and hyperpolarizing bipolar cells, part of the photopic a-wave was eliminated. The PDA-sensitive component, presumed to be due to activity postsynaptic to cones, was responsible for the photopic a-wave threshold and dominated the response over the initial 1 to 1.5 log units of intensity. For brighter stimuli, this component made a constant contribution to the photopic a-wave. A non-PDA-sensitive contribution to the a-wave, presumed to originate directly from cones, was first evident 1 to 1.5 log units above photopic a-wave threshold. It progressively dominated the a-wave at higher intensities, particularly at early time points after the flash. Injecting PDA almost eliminated the photopic a-wave elicited with bright xenon photostrobe flashes that are commonly used for human clinical ERG diagnostic testing, indicating that this a-wave may contain significant postreceptoral activity. CONCLUSION: The primate photopic ERG a-wave derives, in part, from retinal activity postsynaptic to cone photoreceptors, particularly for stimuli near the photopic ERG threshold that are typically used for human clinical studies.

Aminobutyrates↗

PubMed2006

The temporal structure of transient ON/OFF ganglion cell responses and its relation to intra-retinal processing.

A subpopulation of transient ON/OFF ganglion cells in the turtle retina transmits changes in stimulus intensity as series of distinct spike events. The temporal structure of these event sequences depends systematically on the stimulus and thus carries information about the preceding intensity change. To study the spike events' intra-retinal origins, we performed extracellular ganglion cell recordings and simultaneous intracellular recordings from horizontal and amacrine cells. Based on these data, we developed a computational retina model, reproducing spike event patterns with realistic intensity dependence under various experimental conditions. The model's main features are negative feedback from sustained amacrine onto bipolar cells, and a two-step cascade of ganglion cell suppression via a slow and a fast transient amacrine cell. Pharmacologically blocking glycinergic transmission results in disappearance of the spike event sequence, an effect predicted by the model if a single connection, namely suppression of the fast by the slow transient amacrine cell, is weakened. We suggest that the slow transient amacrine cell is glycinergic, whereas the other types release GABA. Thus, the interplay of amacrine cell mediated inhibition is likely to induce distinct temporal structure in ganglion cell responses, forming the basis for a temporal code.

Action Potentials↗