Characteristics Of Retinal Ganglion Cells Research Articles

The response of retinal ganglion cells to optical defocused visual stimuli in mouse retinas

Myopia and astigmatism are two primary types of refractive errors characterized by inaccurate focusing images on the retina. This study aimed to investigate the response characteristics of Retinal Ganglion Cells (RGCs), represented by alpha (α) RGCs, when exposed to focused, simulated spherically defocused images and astigmatically defocused images projected onto mouse retinas.Negative pressure was applied to stretch the soma of RGC in vitro to simulate myopia using a 7–8 μm diameter glass microelectrode, resulting in a 5% increase in the cell's diameter. A custom-made device was utilized to project spherically (equal to ±10 and ± 20 D) and astigmatically (+6.00 D) defocused images onto the retinas. As a control for a deficient intact retinal circuit, αRGCs of connexin 36 knockout (Cx36 KO) mice were used.The response of αRGCs varied significantly in terms of spikes, excitatory postsynaptic currents (EPSCs) and capacitances under stretching conditions to mimic myopia. Significant differences in the amplitudes of EPSCs were observed in the majority of αRGCs when exposed to focused and spherically defocused images in normal and mechanically simulated myopic retinas. However, this difference was not observed in αRGCs of Cx36 KO mice. αRGCs demonstrated significant differences in response between focused and astigmatically defocused images. Once again, αRGCs of Cx36 KO mice did not display differences.αRGCs have the ability to detect focused, spherically, and astigmatically defocused images and exhibit differential responses ex vivo. Gap junction subunit Cx36 may play a crucial role in transmitting visual signals associated with developing and perceiving refractive errors.

Image Contour Detection Based on Visual Pathway Information Transfer Mechanism

Based on the coding mechanism and interactive features of visual information in the visual pathway, a new method of image contour detection is proposed. Firstly, simulating the visual adaptation characteristics of retinal ganglion cells, an adaptation & sensitization regulation model (ASR) based on the adaptation-sensitization characteristics is proposed, which introduces a sinusoidal function curve modulated by amplitude, frequency and initial phase to dynamically adjusted color channel response information and enhance the response of color edges. Secondly, the color antagonism characteristic is introduced to process the color edge responses, and the obtained primary contour responses is fed forward to the dorsal pathway across regions. Then, the coding characteristics of the “angle” information in the V2 region are simulated, and a double receptive fields model (DRFM) is constructed to compensate for the missing detailed contours in the generation of primary contour responses. Finally, a new double stream information fusion model (DSIF) is proposed, which simulates the dorsal overall contour information flow by the across-region response weighted fusion mechanism, and introduces the multi-directional fretting to simulate the fine-tuning characteristics of ventral detail features simultaneously, extracting the significant contours by weighted fusion of dorsal and ventral information streams. In this paper, the natural images in BSDS500 and NYUD datasets are used as experimental data, and the average optimal F-score of the proposed method is 0.72 and 0.69, respectively. The results show that the proposed method has better results in texture suppression and significant contour extraction than the comparison method.

Structural Covariance and Heritability of the Optic Tract and Primary Visual Cortex in Living Human Brains.

Individual differences among human brains exist at many scales, spanning gene expression, white matter tissue properties, and the size and shape of cortical areas. One notable example is an approximately 3-fold range in the size of human primary visual cortex (V1), a much larger range than is found in overall brain size. A previous study (Andrews et al., 1997) reported a correlation between optic tract (OT) cross-section area and V1 size in postmortem human brains, suggesting that there may be a common developmental mechanism for multiple components of the visual pathways. We evaluated the relationship between properties of the OT and V1 in a much larger sample of living human brains by analyzing the Human Connectome Project (HCP) 7 Tesla Retinotopy Dataset (including 107 females and 71 males). This dataset includes retinotopic maps measured with functional MRI (fMRI) and fiber tract data measured with diffusion MRI (dMRI). We found a negative correlation between OT fractional anisotropy (FA) and V1 surface area (r = -0.19). This correlation, although small, was consistent across multiple dMRI datasets differing in acquisition parameters. Further, we found that both V1 surface area and OT properties were correlated among twins, with higher correlations for monozygotic (MZ) than dizygotic (DZ) twins, indicating a high degree of heritability for both properties. Together, these results demonstrate covariation across individuals in properties of the retina (OT) and cortex (V1) and show that each is influenced by genetic factors.SIGNIFICANCE STATEMENT The size of human primary visual cortex (V1) has large interindividual differences. These differences do not scale with overall brain size. A previous postmortem study reported a correlation between the size of the human optic tract (OT) and V1. In this study, we evaluated the relationship between the OT and V1 in living humans by analyzing a neuroimaging dataset that included functional MRI (fMRI) and diffusion MRI (dMRI) data. We found a small, but robust correlation between OT tissue properties and V1 size, supporting the existence of structural covariance between the OT and V1 in living humans. The results suggest that characteristics of retinal ganglion cells (RGCs), reflected in OT measurements, are correlated with individual differences in human V1.

Explore the molecular mechanism of angle-closure glaucoma in elderly patients induced telomere shortening of retinal ganglion cells through oxidative stress

Senile glaucoma is a common ophthalmological disease in the elderly. It is a disease of visual papillary perfusion caused by elevated intraocular pressure, complicated by visual dysfunction. Glaucoma can cause serious damage to the normal vision of the elderly. Therefore, exploring the related molecular mechanisms of glaucoma is of great significance to the diagnosis and treatment of glaucoma. This is an exploratory study. Establish a mouse model and conduct experimental groupings. After one week of adaptive feeding, the mice were intraperitoneally injected with an anesthetic mixture: ketamine + xylazine. Then the mice were sacrificed by neck dissection, and the eyeball tissues were immediately dissected. HE staining was used to analyze the histopathological characteristics of the retina of each group of mice. MitoSOX fluorescent probe was used to analyze the content of ROS in retinal tissue. The ELISA analysis was used to detect the activation of β-galactosidase for the aging characteristics of retinal ganglion cells in retinal tissues. Immunohistochemistry experiments were used to analyze the expression of telomerase TERT in retinal tissues. Western blot analysis was used to determine the expression of proteins POT1, TERF1, TERF2, and TINF2 in retinal tissues. The HE staining experiment showed that the damage of retinal tissue decreased from group Glaucoma to group Old, group Old to group Young. The experimental results of MitoSOX fluorescent probe show that ROS content is positively correlated with the degree of tissue damage. ELISA analysis results showed that the expression trend of β-galactosidase was the same as the ROS content. The protein expression levels related to telomere protection (TRET, POT1, TREF1, TREF2 and TINF2) all increased from group Glaucoma to group Old, group Old to group Young. The increase in ROS content, the decrease in telomere protection-related protein expression (telomere shortening) induced by ROS, and the increase of the expression of β-galactosidase, are all potential molecular mechanisms for the occurrence of angle-closure glaucoma in elderly patients.

Efficient stimulation of retinal regeneration from Müller glia in adult mice using combinations of proneural bHLH transcription factors.

Regenerative neuroscience aims to stimulate endogenous repair in the nervous system to replace neurons lost from degenerative diseases. Recently, we reported that overexpressing the transcription factor Ascl1 in Müller glia (MG) is sufficient to stimulate MG to regenerate functional neurons in the adult mouse retina. However, this process is inefficient, and only a third of the Ascl1-expressing MG generate new neurons. Here, we test whether proneural transcription factors of the Atoh1/7 class can further promote the regenerative capacity of MG. We find that the combination of Ascl1:Atoh1 is remarkably efficient at stimulating neurogenesis, even in the absence of retinal injury. Using electrophysiology and single-cell RNA sequencing (scRNA-seq), we demonstrate that Ascl1:Atoh1 generates a diversity of retinal neuron types, with the majority expressing characteristics of retinal ganglion cells. Our results provide a proof of principle that combinations of developmental transcription factors can substantially improve glial reprogramming to neurons and expand the repertoire of regenerated cell fates.

Functional characterization of retinal ganglion cells using tailored nonlinear modeling

The mammalian retina encodes the visual world in action potentials generated by 20–50 functionally and anatomically-distinct types of retinal ganglion cell (RGC). Individual RGC types receive synaptic input from distinct presynaptic circuits; therefore, their responsiveness to specific features in the visual scene arises from the information encoded in synaptic input and shaped by postsynaptic signal integration and spike generation. Unfortunately, there is a dearth of tools for characterizing the computations reflected in RGC spike output. Therefore, we developed a statistical model, the separable Nonlinear Input Model, to characterize the excitatory and suppressive components of RGC receptive fields. We recorded RGC responses to a correlated noise (“cloud”) stimulus in an in vitro preparation of mouse retina and found that our model accurately predicted RGC responses at high spatiotemporal resolution. It identified multiple receptive fields reflecting the main excitatory and suppressive components of the response of each neuron. Significantly, our model accurately identified ON-OFF cells and distinguished their distinct ON and OFF receptive fields, and it demonstrated a diversity of suppressive receptive fields in the RGC population. In total, our method offers a rich description of RGC computation and sets a foundation for relating it to retinal circuitry.

Contrast sensitivity reveals an oculomotor strategy for temporally encoding space

The contrast sensitivity function (CSF), how sensitivity varies with the frequency of the stimulus, is a fundamental assessment of visual performance. The CSF is generally assumed to be determined by low-level sensory processes. However, the spatial sensitivities of neurons in the early visual pathways, as measured in experiments with immobilized eyes, diverge from psychophysical CSF measurements in primates. Under natural viewing conditions, as in typical psychophysical measurements, humans continually move their eyes even when looking at a fixed point. Here, we show that the resulting transformation of the spatial scene into temporal modulations on the retina constitutes a processing stage that reconciles human CSF and the response characteristics of retinal ganglion cells under a broad range of conditions. Our findings suggest a fundamental integration between perception and action: eye movements work synergistically with the spatio-temporal sensitivities of retinal neurons to encode spatial information.

Suboptimal eye movements for seeing fine details.

Human eyes are never stable, even during attempts of maintaining gaze on a visual target. Considering transient response characteristics of retinal ganglion cells, a certain amount of motion of the eyes is required to efficiently encode information and to prevent neural adaptation. However, excessive motion of the eyes leads to insufficient exposure to the stimuli, which creates blur and reduces visual acuity. Normal miniature eye movements fall in between these extremes, but it is unclear if they are optimally tuned for seeing fine spatial details. We used a state-of-the-art retinal imaging technique with eye tracking to address this question. We sought to determine the optimal gain (stimulus/eye motion ratio) that corresponds to maximum performance in an orientation-discrimination task performed at the fovea. We found that miniature eye movements are tuned but may not be optimal for seeing fine spatial details.

Decorrelation of retinal response to natural scenes by fixational eye movements

Under natural viewing conditions the input to the retina is a complex spatiotemporal signal that depends on both the scene and the way the observer moves. It is commonly assumed that the retina processes this input signal efficiently by taking into account the statistics of the natural world. It has recently been argued that incessant microscopic eye movements contribute to this process by decorrelating the input to the retina. Here we tested this theory by measuring the responses of the salamander retina to stimuli replicating the natural input signals experienced by the retina in the presence and absence of fixational eye movements. Contrary to the predictions of classic theories of efficient encoding that do not take behavior into account, we show that the response characteristics of retinal ganglion cells are not sufficient in themselves to disrupt the broad correlations of natural scenes. Specifically, retinal ganglion cells exhibited strong and extensive spatial correlations in the absence of fixational eye movements. However, the levels of correlation in the neural responses dropped in the presence of fixational eye movements, resulting in effective decorrelation of the channels streaming information to the brain. These observations confirm the predictions that microscopic eye movements act to reduce correlations in retinal responses and contribute to visual information processing.

Organotypic culture of neural retina as a research model of neurodegeneration of ganglion cells

Organotypic models deserve special attention among the large variety of methods of vertebrate retina cultivation. The purpose of this study was to make a detailed qualitative and quantitative characterization of a model employing roller organotypic cultivation of the neural retina of rat eye posterior segment, with special attention to morphological and functional characteristics of retinal ganglion cells. The study included morphological analysis of retina histological preparations as well as estimation of RNA synthesis and evaluation of neuron survival by the Brachet and TUNEL methods, respectively. Retina has been shown to display normal morphofunctional characteristics for the first 12 h of cultivation. After 24 h, a substantial number of ganglion cells underwent pyknosis and stopped RNA synthesis. Almost all the cells of the retinal ganglion layer became apoptotic by 3-4 days in vitro. In the course of cultivation, neural retina is detached from the underlying layers of the posterior eye segment and undergoes significant cytoarchitectonic changes. The causes of ganglion cell death during organotypic cultivation of eye posterior segment are discussed. This method can serve as a suitable model for the screening of new retinoprotectors and for research on ganglion cell death resulting from retina degenerative diseases, e.g. glaucoma.

Light-Evoked Currents in Retinal Ganglion Cells from Dystrophic RCS Rats

Purpose: To study the electrophysiological properties of the light-evoked currents in ganglion cells in situations of retinal degeneration. Methods: We investigated light-evoked currents in ganglion cells by performing whole-cell patch-clamp recordings from ganglion cells using a retina-stretched preparation from Royal College of Surgeons (RCS) rats, a model of retinal degeneration and congenic controls at different ages. Pharmacological inhibitors of the AMPA receptor (NBQX), GABA receptor (BMI), and sodium channels (TTX) were used to identify the components of the light-evoked currents in ON, OFF and ON-OFF retinal ganglion cells. Results: We found that the light-evoked currents in ganglion cells from control rats were inhibited by NBQX, BMI and TTX, suggesting that AMPA receptors, GABA receptors and sodium channels contribute to these currents in ganglion cells. However, only AMPA receptor-mediated currents were recorded in RCS rats. Light-evoked inward currents were absent in the majority of ganglion cells from RCS rats, particularly at the later stages of retinal degeneration. At earlier stages of retinal degeneration, we found that both the timing and amplitude of light-evoked currents are significantly different in ganglion cells from RCS and control rats. Conclusions: Our study furthers the understanding of the electrophysiological characteristics of retinal ganglion cells during retinal degeneration, and provides insight into the optimal timing for the treatment of retinal degeneration.

Modeling a space-variant cortical representation for apparent motion

Receptive field sizes of neurons in early primate visual areas increase with eccentricity, as does temporal processing speed. The fovea is evidently specialized for slow, fine movements while the periphery is suited for fast, coarse movements. In either the fovea or periphery discrete flashes can produce motion percepts. Grossberg and Rudd (1989) used traveling Gaussian activity profiles to model long-range apparent motion percepts. We propose a neural model constrained by physiological data to explain how signals from retinal ganglion cells to V1 affect the perception of motion as a function of eccentricity. Our model incorporates cortical magnification, receptive field overlap and scatter, and spatial and temporal response characteristics of retinal ganglion cells for cortical processing of motion. Consistent with the finding of Baker and Braddick (1985), in our model the maximum flash distance that is perceived as an apparent motion (Dmax) increases linearly as a function of eccentricity. Baker and Braddick (1985) made qualitative predictions about the functional significance of both stimulus and visual system parameters that constrain motion perception, such as an increase in the range of detectable motions as a function of eccentricity and the likely role of higher visual processes in determining Dmax. We generate corresponding quantitative predictions for those functional dependencies for individual aspects of motion processing. Simulation results indicate that the early visual pathway can explain the qualitative linear increase of Dmax data without reliance on extrastriate areas, but that those higher visual areas may serve as a modulatory influence on the exact Dmax increase.

When are microcircuits well-modeled by maximum entropy methods?

We consider systems of three spiking cells, driven by a common fluctuating input against independent background noise. The cells are chosen to be either simple sum-and-threshold units, linear integrate and fire, or nonlinear (fitted to spiking characteristics of retinal ganglion cells) integrate and fire. The inputs are chosen from distributions that are either gaussian, uniform, skewed, or bimodal. For each circuit, we compute the distribution on output spiking states either analytically or by sampling, approximate by a maximum entropy fit, and measure the goodness of fit via the Kullback-Leibler divergence between the two. We repeat over a range of input parameters: mean, total input variance, and the relative strength of common drive to background noise. Results In analytical studies, we identified a simple “consistency” condition relating the probabilities of various network states that must hold if network outputs are to be perfectly described by a PME distribution. The consistency condition indeed is approximately satisfied, and the activity of this circuit is well-modeled by the PME fit, if the inputs are unimodal. This is in agreement with the results of [3,4] in the gaussian case, but it extends beyond gaussian inputs. Indeed, this result holds regardless of whether spike generation is characterized by a simple static nonlinearity, or by integrate-and-fire (LIF) threshold-crossing dynamics. However, this circuit does generate substantial higher-order correlations if the common input to the three cells is bimodal. This approach complements the distinct expansions in [5], enabling instead a geometric picture of “regions” of network output statistics expected that will produce the strongest deviations from pairwise descriptions. Finally we address the question of whether the goodness-of-fit of the PME approximation is informative about network architecture. We have already seen that high order inputs do not imply deviations from the PME fit. To examine the converse question, we study a simple circuit driven by pairwise bimodal inputs. We find thatthis circuit can generate significant deviations from the PME fit, despite the pairwise anatomical projections.

The Hermann Grid Illusion Revisited

The Hermann grid illusion consists of smudges perceived at the intersections of a white grid presented on a black background. In 1960 the effect was first explained by a theory advanced by Baumgartner suggesting the illusory effect is due to differences in the discharge characteristics of retinal ganglion cells when their receptive fields fall along the intersections versus when they fall along non-intersecting regions of the grid. Since then, others have claimed that this theory might not be adequate, suggesting that a model based on cortical mechanisms is necessary [Lingelbach et al, 1985 Perception 14(1) A7; Spillmann, 1994 Perception 23 691 708; Geier et al, 2004 Perception 33 Supplement, 53; Westheimer, 2004 Vision Research 44 2457 2465]. We present in this paper the following evidence to show that the retinal ganglion cell theory is untenable: (i) varying the makeup of the grid in a manner that does not materially affect the putative differential responses of the ganglion cells can reduce or eliminate the illusory effect; (ii) varying the grid such as to affect the putative differential responses of the ganglion cells does not eliminate the illusory effect; and (iii) the actual spatial layout of the retinal ganglion cell receptive fields is other than that assumed by the theory. To account for the Hermann grid illusion we propose an alternative theory according to which the illusory effect is brought about by the manner in which S1 type simple cells (as defined by Schiller et al, 1976 Journal of Neurophysiology 39 1320-1333) in primary visual cortex respond to the grid. This theory adequately handles many of the facts delineated in this paper.

Theoretical reproduction of perceptual responses to drifting image using a spatio-temporal human vision model with a multiple-channel structure

A human vision model with a multiple-channel structure that can quantitatively simulate spatio-temporal perceptual responses to flickering sinusoidal waves as well as still images has already been proposed. This model was mathematically formulated as an adaptive focus adjustable feedback system based on two essential properties of the human vision system: the interdependent relationship between a retinal image's blur and a visual field size; and the spatio-temporal response characteristics of retinal ganglion cells. However, as the latter characteristics were actually formulated by utilizing spatio-temporal frequency characteristics experimentally measured using flickering sinusoidal waves, it is very important to confirm the model's applicability to images whose temporal change characteristics differ from flickering images. This paper discusses the model's applicability to drifting sinusoidal waves, which have a typical kind of temporal change characteristic except for flickering images. Consequently, it was clarified that the model's spatial frequency characteristics of contrast sensitivity and those of optimum drifting speed are in good agreement with experimental data. These results suggest that this model is also applicable to images with various kinds of temporal change characteristics other than flickering patterns. This provides the model's validity or generality. Moreover, the model was applied to the theoretical prediction of perceptual response characteristics of drifting square waves. How drifting square waves were perceived is also discussed. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 3, 80(2): 35–45, 1997

Theoretical reproduction of perceptual responses to drifting image using a spatio‐temporal human vision model with a multiple‐channel structure

A human vision model with a multiple-channel structure that can quantitatively simulate spatio-temporal perceptual responses to flickering sinusoidal waves as well as still images has already been proposed. This model was mathematically formulated as an adaptive focus adjustable feedback system based on two essential properties of the human vision system: the interdependent relationship between a retinal image's blur and a visual field size; and the spatio-temporal response characteristics of retinal ganglion cells. However, as the latter characteristics were actually formulated by utilizing spatio-temporal frequency characteristics experimentally measured using flickering sinusoidal waves, it is very important to confirm the model's applicability to images whose temporal change characteristics differ from flickering images. This paper discusses the model's applicability to drifting sinusoidal waves, which have a typical kind of temporal change characteristic except for flickering images. Consequently, it was clarified that the model's spatial frequency characteristics of contrast sensitivity and those of optimum drifting speed are in good agreement with experimental data. These results suggest that this model is also applicable to images with various kinds of temporal change characteristics other than flickering patterns. This provides the model's validity or generality. Moreover, the model was applied to the theoretical prediction of perceptual response characteristics of drifting square waves. How drifting square waves were perceived is also discussed. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 3, 80(2): 35–45, 1997

Generation of cell lines from embryonic quail retina capable of mature neuronal differentiation.

The avian embryonic retina is widely used as a model system for cellular and molecular studies on central nervous system neurons. We aimed at the generation of cell lines from the early embryonic quail retina by retroviral oncogene transduction. For this, we made use of the retina organ culture system which exhibits both proliferation, necessary for stable oncogene transduction, and initial neuronal differentiation, a prerequisite for the generation of cell lines with mature neuronal properties. The oncogene myc was chosen as it is both proliferation-inducing and differentiation-compatible. A chimeric gene, mycER, containing v-myc and the hormone-binding domain of the estrogen receptor, was used for transduction in order to allow for hormone regulation of myc activity. Transduced organ-cultured cells from temporal and nasal retina were passaged into sparse single cell cultures. From these, colonies of rapidly dividing cells were isolated and the progeny expanded as cell lines. The lines contained cells with features of neuroepithelial cells, showing vimentin and A2B5. They also contained spontaneously differentiated neuronal cells showing neurofilament L and N-CAM180. A subpopulation of the neuronal cells exhibited the morphological characteristics of retinal ganglion cells, i.e., large pear-shaped somata each emitting one long process with a distinct growth cone. In addition, they showed the marker profile of retinal ganglion cells, i.e., expression of Thy-1, G4, DM-GRASP, Nr-CAM, neurofilament H, and tau. Neuronal differentiation could be induced by the addition of db cAMP and retinoic acid. The mature neuronal features of the lines open new possibilities to study properties of retinal neurons, including ganglion cells, in a defined and manipulable experimental system.

Anatomical characterization of retinal ganglion cells that project to the nucleus of the basal optic root in the turtle ( Pseudemys scripta elegans)

There is little detailed information about retinal ganglion cells which project to specific central targets in the brain. The present study examined retinal ganglion cells projecting to the nucleus of the basal optic root, a major accessory retinal target in the turtle. These ganglion cells were first selectively labeled using retrograde transport of rhodamine injected stereotaxically into the nucleus of the basal optic root. The number and distribution of the retrogradely labeled cells in the retina was then determined. Some of these retrogradely labeled cells were then injected intracellularly with Lucifer Yellow, photoconverted using diaminobenzidine, and drawn in detail using a camera lucida attachment. There were approximately 1500 ganglion cells in each retina which projected to the nucleus of the basal optic root, of which 20% had cell bodies displaced to the inner nuclear layer. More than 50% of the total population was concentrated in the visual streak region. All ganglion cells projecting to the nucleus of the basal optic root, both normal and displaced, had monostratified dendritic arborizations in stratum 1 of the inner plexiform layer. About 41% of these ganglion cells had elongated dendritic arborizations with distinct orientations, which may suggest a correlation of morphology and function. There were similarities in the overall appearance, and in the type and stratification of the dendritic arborizations of all ganglion cells projecting to the nucleus of the basal optic root. These anatomical similarities are consistent with the previously demonstrated similarities in physiology and may reflect a common role for these ganglion cells in visual processing.

The contribution of NMDA and Non-NMDA receptors to the light-evoked input-output characteristics of retinal ganglion cells

To examine how light-evoked excitatory synaptic inputs to retinal ganglion cells are transformed into output patterns of activity, action potentials were recorded with cell-attached patch-clamp techniques, and then EPSCs and EPSPs were recorded from the same cell in the whole-cell configuration. AP7, an NMDA antagonist, reduced the light-evoked peak spike frequency 36% ± 21% (mean ± SD) and reduced the EPSC amplitude, indicating a major role for NMDA receptors in the light response. CNQX, a non-NMDA receptor antagonist, reduced the light-evoked peak spike frequency 28% ± 22%. CNQX also caused a voltage- and magnesium-dependent delay in spike onset. AP7 and CNQX, however, did not differ significantly in their effect on the EPSC time course, indicating that postsynaptic cellular properties are responsible for the delay observed in the presence of CNQX. These results show that the NMDA receptor contribution to the excitatory response is increased as the cell is depolarized from rest by non-NMDA input.

Retrograde labeling, enrichment, and characterization of retinal ganglion cells from the neonatal rat

We have developed a method for labeling retinal ganglion cells in neonatal rats by retrograde transport of the fluorescent dye, True Blue (TB), injected into the optic chiasm. Following proteolytic dissociation of labeled retinas into single cells, the labeled cells could be enriched 50- to 100-fold by centrifugation in a 5%/10% metrizamide gradient. When plated in Ham's F-10 medium in the presence of fetal calf serum and chick optic tectum-conditioned medium, the labeled cells could be maintained in vitro up to 48 hr. In these cultures, the ganglion cells (GCS) constituted 50 to 70% of the total cell population. When GC-rich fractions or GC cultures were stained with a monoclonal antibody to Thy-1 antigen, greater than 90% of the TB-labeled cells were reactive. In order to localize voltage-sensitive sodium channels, GC-rich cultures were reacted with 125I-scorpion toxin. Analysis of the autoradiograms showed that the density of silver grains was about 10-fold higher on TB-labeled cells than on nonfluorescent cells, or in controls which contained excess of unlabeled toxin. When GC cultures were incubated with micromolar concentrations of putative GC transmitters, aspartate and glutamate, the amino acids were accumulated by 15 to 20% of labeled cells. Several lectin receptors were also localized on TB-labeled cells in situ. Whereas the lectins wheat germ agglutinin, concanavalin A, peanut agglutinin, Dolichos biflorus agglutinin, and Limulus polyphemus agglutinin bound to TB-labeled cells, others such as Ricinus communis agglutinin I, Ulex, and Lotus lectins showed no binding. The lectin binding was specific since preincubation with the appropriate hapten sugar blocked lectin binding.