[Electron microscopic studies of the retinal ganglion cell: "subsurface cisterns" in retinal ganglion cells of human and crab-eating monkey (Macaca irus)].
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Distribution of synaptic inputs onto goldfish retinal ganglion cell dendrites.
Retinal ganglion cells in the goldfish were labeled by retrograde transport of horseradish peroxidase, and areas near the optic disk where the dendrites appeared to be completely filled were analyzed by electron microscopy. Only 6% of their inputs were ribbon synapses from bipolar cells; the other 94% of the inputs were conventional synapses mostly or entirely from amacrine cells. There were three strata of the inner plexiform layer with high densities of inputs to ganglion cells, the first centered at approx. 50% and the second at approx. 80% of the inner plexiform layer depth, as measured from the ganglion cell layer to the inner nuclear layer. These two strata comprised 25% of the volume but contained 41% of the inputs to ganglion cells. There were also two strata with very low densities of ganglion cell inputs located near the boundaries of the inner plexiform layer, from 0- to 15% and 90- to 100% of the depth. These strata, which also comprised 25% of the volume, contained only 7% of the inputs to retinal ganglion cells. These strata near the boundaries of the inner plexiform layer also contained 81% of the processes with large, dense-cored vesicles characteristic of peptidergic neurons. We concluded that each of the two sublaminae, a and b, identified previously by physiological criteria, could be further divided into at least two strata, one near the boundary of the inner plexiform layer with abundant peptidergic terminals and very few ganglion cell synapses and another near the center of the inner plexiform layer with numerous ganglion cell synapses. We also propose a hypothesis that could explain the functions of these additional strata.
Animals↗
Effects of cholinergic drugs on receptive field properties of rabbit retinal ganglion cells.
1. Retinal ganglion cells were recorded extracellularly from the rabbit's eye in situ to study the effects of cholinergic drugs on receptive field properties. Physostigmine, an acetylcholinesterase inhibitor, and nicotine increased the spontaneous activity of nearly all retinal ganglion cell types. The effectiveness of physostigmine was roughly correlated with the neurone's inherent level of spontaneous activity. Brisk cells, having high rates of spontaneous firing, showed large increases in their maintained discharge, whereas sluggish cells, with few or no spontaneous spikes, showed small and sometimes transient increases in spontaneous activity during physostigmine.2. The sensitivity of ganglion cells to spots of optimal size and position did not change substantially during the infusion of physostigmine. However, the responsiveness to light (number of spikes per stimulus above the spontaneous level) increased. This effect occurred with sluggish and more complex cells, rarely with brisk cells.3. Another effect of physostigmine on sluggish and more complex cells was to make these cells ;on-off'. The additional response to the inappropriate change in contrast had a long latency and lacked an initial transient burst.4. Complex receptive field properties such as orientation sensitivity, radial grating inhibition, speed tuning and size specificity were also examined. These inhibitory properties were still present during infusion of physostigmine and, in most cases, the trigger feature of each cell type remained.5. These results are consistent with pharmacological results on ACh release from the retina. There appear to be two types of release of ACh, having their most powerful influences on separate classes of cells. One release (transient), occurs at light onset and offset and acts primarily on sluggish and more complex ganglion cells; the other release (tonic) is not light-modulated and acts primarily on brisk cells. A wiring diagram for the ACh cells is suggested.
Acetylcholine↗
Postnatal innervation of the rat superior colliculus by axons of late-born retinal ganglion cells.
Rat retinal ganglion cells (RGCs) are generated between embryonic day (E) 13 and E19. Retinal axons first reach the superior colliculus at E16/16.5 but the time of arrival of axons from late-born RGCs is unknown. This study examined (i) whether there is a correlation between RGC genesis and the timing of retinotectal innervation and (ii) when axons of late-born RGCs reach the superior colliculus. Pregnant Wistar rats were injected intraperitoneally with bromodeoxyuridine (BrdU) on E16, E18 or E19. Pups from these litters received unilateral superior colliculus injections of fluorogold (FG) at ages between postnatal (P) day P0 and P6, and were perfused 1-2 days later. RGCs in 3 rats from each BrdU litter were labelled in adulthood by placing FG onto transected optic nerve. Retinas were cryosectioned and the number of FG, BrdU and double-labelled (FG+/BrdU+) RGCs quantified. In the E16 group, the proportion of FG-labelled RGCs that were BrdU+ did not vary with age, indicating that axons from these cells had reached the superior colliculus by P0/P1. In contrast, for the smaller cohorts of RGCs born on E18 or E19, the proportion of BrdU+ cells that were FG+ increased significantly after birth; axons from most RGCs born on E19 were not retrogradely FG-labelled until P4/P5. Thus there is a correlation between birthdate and innervation in rat retinotectal pathways. Furthermore, compared to the earliest born RGCs, axons from late-born RGCs take about three times longer to reach the superior colliculus. Later-arriving axons presumably encounter comparatively different growth terrains en route and eventually innervate more differentiated target structures.
Animals↗
Proportions of ON-center versus OFF-center cells in retinal ganglion cells with regenerated axons of adult cats.
Axons of retinal ganglion cells (RGCs) of adult cats were transected and regenerated by the transplantation of peripheral nerves. Two months after transplantation dendritic arbors of RGCs with regenerated axons (r-RGCs) were visualized with intracellular injections of horseradish peroxidase (HRP). The HRP-filled r-RGCs were classified as alpha, beta, gamma, or unclassified cells. The r-RGCs were then sectioned vertically and their dendritic ramification in the inner plexiform layer (IPL) was examined to distinguish them as OFF- or ON-center cells. Seventy-nine cells extended their dendrites into either sublamina a (OFF) or sublamina b (ON) of the IPL. Two gamma cells spread dendrites into both ON and OFF sublaminae. The numbers of ON-center cells were greater than those of OFF-center cells in three classes: 22 of 24 beta cells, 4 of 6 gamma cells, and 16 of 18 unclassified cells. These data confirmed the predominance of ON-center cells among X/beta and W cells in previous physiological recordings from regenerated axons of r-RGCs. However, only 4 cells were ON-center among 33 r-RGCs with alpha cell morphology. The result apparently conflicts with the predominance of ON-center Y cells in physiological sampling. Possible explanations for the apparent discrepancy are discussed.
Animals↗
Homotypic constraints dominate positioning of on- and off-center beta retinal ganglion cells.
Beta retinal ganglion cells (RGCs) of the cat are classified as either on-center or off-center, according to their response to light. The cell bodies of these on- and off-center RGCs are spatially distributed into regular patterns, known as retinal mosaics. In this paper, we investigate the nature of spatial dependencies between the positioning of on- and off-center RGCs by analysing maps of RGCs and simulating these patterns. We introduce principled approaches to parameter estimation, along with likelihood-based techniques to evaluate different hypotheses. Spatial constraints between cells within-type and between-type are assumed to be controlled by two univariate interaction functions and one bivariate interaction function. By making different assumptions on the shape of the bivariate interaction function, we can compare the hypothesis of statistical independence against the alternative hypothesis of functional independence, where interactions between type are limited to preventing somal overlap. Our findings suggest that the mosaics of on- and off-center beta RGCs are likely to be generated assuming functional independence between the two types. By contrast, allowing a more general form of bivariate interaction function did not improve the likelihood of generating the observed maps. On- and off-center beta RGCs are therefore likely to be positioned subject only to homotypic constraints and the physical constraint that no two somas of opposite type can occupy the same position.
Algorithms↗
Neurite outgrowth in retinal ganglion cell culture.
Retinal ganglion cells (RGC) are the projection neurons of the eye. The RGC is the primary cell type injured in a variety of diseases of the optic nerve, including glaucoma and optic neuritis. The most well-established extrinsic signal of RGC survival and axonal outgrowth is the neurotrophin brain-derived neurotrophic factor. An immunopurification system has been adapted in order to filter large enough quantities of RGCs from the mixed population of retinal neurons in order to perform high-throughput screening in a 96-well format. Using this assay, the screening of a combinatorial chemical library for compounds with a similar effect to brain-derived neurotrophic factor may be preformed. Follow-up validation studies are performed by evaluating for a dose-response relationship.
Animals↗
Quantal encoding of information in a retinal ganglion cell.
A retinal ganglion cell receives information about a white-noise stimulus as a flickering pattern of glutamate quanta. The ganglion cell reencodes this information as brief bursts of one to six spikes separated by quiescent periods. When the stimulus is repeated, the number of spikes in a burst is highly reproducible (variance < mean) and spike timing is precise to within 10 ms, leading to an estimate that each spike encodes about 2 bits. To understand how the ganglion cell reencodes information, we studied the quantal patterns by repeating a white-noise stimulus and recording excitatory currents from a voltage-clamped, brisk-sustained ganglion cell. Quanta occurred in synchronous bursts of 3 to 65; the resulting postsynaptic currents summed to form excitatory postsynaptic currents (EPSCs). The number of quanta in an EPSC was only moderately reproducible (variance = mean), quantal timing was precise to within 14 ms, and each quantum encoded 0.1-0.4 bit. In conclusion, compared to a spike, a quantum has similar temporal precision, but is less reproducible and encodes less information. Summing multiple quanta into discrete EPSCs improves the reproducibility of the overall quantal pattern and contributes to the reproducibility of the spike train.
Action Potentials↗
Inhibitory network properties shaping the light evoked responses of cat alpha retinal ganglion cells.
Cat retinal ganglion cells of the Y (or alpha) type respond to luminance changes opposite those preferred by their receptive-field centers with a transient hyperpolarization. Here, we examine the spatial organization and synaptic basis of this light response by means of whole-cell current-clamp recordings made in vitro. The hyperpolarization was largest when stimulus spots approximated the size of the receptive-field center, and diminished substantially for larger spots. The hyperpolarization was largely abolished by bath application of strychnine, a blocker of glycinergic inhibition. Picrotoxin, an antagonist of ionotropic GABA receptors, greatly reduced the attenuation of the hyperpolarizing response for large spots. The data are consistent with a model in which (1) the hyperpolarization reflects inhibition by glycinergic amacrine cells of bipolar terminals presynaptic to the alpha cells, and perhaps direct inhibition of the alpha cell as well; and (2) the attenuation of the hyperpolarization by large spots reflects surround inhibition of the glycinergic amacrine by GABAergic amacrine cells. This circuitry may moderate nonlinearities in the alpha-cell light response and could account for some excitatory and inhibitory influences on alpha cells known to arise from outside the classical receptive field.
Amacrine Cells↗
Neurotrophic factors and depolarization do not enhance viability and process regrowth on a purified set of chick embryo retinal ganglion cells.
As retinal ganglion cells (RGCs) develop, the amount of membrane glycoprotein Thy-1 increases, consequently, the RGC binding to Thy-1 antibody enlarges. This phenomenon sustained Thy-1 panning purification of two sets: loose bound cells (LBCs); and tight bound cells (TBCs). Thy-1, neurofilament and growth associated protein-43 characterized both sets as RGCs, but the expression of RA4 antigen and gangliotetraosylgangliosides distinguished LBCs as immature and TBCs as mature. The cell composition in 4-day TBC cultures remained unchanged as immunocharacterization indicated. These cells survived and regrew their processes in plain medium, however, trophic factors (TFs) and depolarization did not enhance their development. This peculiar behavior might be due to their neural maturity, whereas in LBC cultures, TFs produced positive effects.
Animals↗
The dynamics of primate M retinal ganglion cells.
The retinal ganglion cells (RGCs) of the primate form at least two classes--M and P--that differ fundamentally in their functional properties. M cells have temporal-frequency response characteristics distinct from P cells (Benardete et al., 1992; Lee et al., 1994). In this paper, we elaborate on the temporal-frequency responses of M cells and focus in detail on the contrast gain control (Shapley & Victor, 1979a,b). Earlier data showed that the temporal-frequency response of M cells is altered by the level of stimulus contrast (Benardete et al., 1992). Higher contrast shifts the peak of the frequency-response curve to higher temporal frequency and produces a phase advance. In this paper, by fitting the data to a linear filter model, the effect of contrast on the temporal-frequency response is subsumed into a change in a single parameter in the model. Furthermore, the model fits are used to predict the response of M cells to steps of contrast, and these predictions demonstrate the dynamic effect of contrast on the M cells' response. We also present new data concerning the spatial organization of the contrast gain control in the primate and show that the signal that controls the contrast gain must come from a broadly distributed network of small subunits in the surround of the M-cell receptive field.
Animals↗
The emerging role of proteases in retinal ganglion cell death.
Retinal ganglion cell (RGC) death is an important issue in Primary Open Angle-Glaucoma (POAG) in terms of both vision loss and health care costs. Yet, the pathophysiology underlying RGC death in glaucoma is unclear. A growing body of evidence indicates that proteases that modulate the extracellular matrix (ECM) milieu in the retina, either directly or indirectly, play an important role in dictating the fate of RGCs. Recent evidence indicates that proteases, in addition to ECM-remodeling, have broader functional roles in glutamate receptor processing and predisposing RGCs to secondary damage. This review is focused on discussing the role of two groups of proteases, the matrix metalloproteinases (MMPs) and the plasminogen activators (PAs), in RGC death. In a long-run, a better understanding of the mechanisms involved in the regulation of proteases may lead to the development of adjunctive treatment options to attenuate RGC death and improve vision loss in glaucoma.
Animals↗
Receptive field structure-function correlates in developing turtle retinal ganglion cells.
Mature retinal ganglion cells (RGCs) have distinct morphologies that often reflect specialized functional properties such as On and Off responses. But the structural correlates of many complex receptive field (RF) properties (e.g. responses to motion) remain to be deciphered. In this study, we have investigated whether motion anisotropies (non-homogeneities) characteristic of embryonic turtle RGCs arise from immature dendritic arborization in these cells. To test this hypothesis, we have looked at structure-function correlates of developing turtle RGCs from Stage 23 (S23) when light responses emerge, until 15 weeks post-hatching (PH). Using whole cell patch clamp recordings, RGCs were labelled with Lucifer Yellow (LY) while recording their responses to moving edges of light. Comparison of RF and dendritic arbor layouts revealed a weak correlation. To obtain a larger structural sample of developing RGCs, we have looked at dendritic morphology in RGCs retrogradely filled with the tracer horseradish peroxidase (HRP) from S22 (when RGCs become spontaneously active, shortly before they become sensitive to light) until two weeks PH. We found that there was intense dendritic growth from S22 onwards, reaching peak proliferation at S25 (a week before hatching), while RGCs are still exhibiting significant motion anisotropies. Based on these observations, we suggest that immature anisotropic RGC RFs must originate from sparse synaptic inputs onto RGCs rather than from the immaturity of their growing dendritic trees.
Action Potentials↗
Single cell RT-PCR analysis of tyrosine kinase receptor expression in adult rat retinal ganglion cells isolated by retinal sandwiching.
We describe a protocol for analysis of gene expression in single, acutely dissociated adult rat retinal ganglion cells using RT-PCR. Retrograde tracing of retinal ganglion cells from the superior colliculi was conducted using Fluorogold. Retinas were dissected and ganglion cells isolated using retinal layer separation (sandwiching). Single, fluorescently labelled retinal ganglion cells were aspirated using a micropipette and used for PCR. Two PCR protocols are described where single cell cDNA was analysed for TrkB and GAPDH or TrkB, TrkC, Ret, Met, ErbB2 and Beta-actin by multiplex-PCR. All five tyrosine kinase receptors were amplified from single retinal ganglion cells. The method will prove useful for the molecular characterization of adult retinal ganglion cells.
Animals↗
Rat optic nerve oligodendrocytes develop in the absence of viable retinal ganglion cell axons.
Retinal ganglion cell axons and axonal electrical activity have been considered essential for migration, proliferation, and survival of oligodendrocyte lineage cells in the optic nerve. To define axonal requirements during oligodendrogenesis, the developmental appearance of oligodendrocyte progenitors and oligodendrocytes were compared between normal and transected optic nerves. In the absence of viable axons, oligodendrocyte precursors migrated along the length of the nerve and subsequently multiplied and differentiated into myelin basic protein-positive oligodendrocytes at similar densities and with similar temporal and spatial patterns as in control nerves. Since transected optic nerves failed to grow radially, the number of oligodendrocyte lineage cells was reduced compared with control nerves. However, the mitotic indices of progenitors and the percentage of oligodendrocytes undergoing programmed cell death were similar in control and transected optic nerves. Oligodendrocytes lacked their normal longitudinal orientation, developed fewer, shorter processes, and failed to form myelin in the transected nerves. These data indicate that normal densities of oligodendrocytes can develop in the absence of viable retinal ganglion axons, and support the possibility that axons assure their own myelination by regulating the number of myelin internodes formed by individual oligodendrocytes.
Animals↗
Hypothermia of 8 degrees C protects cultured retinal pigment epithelial cells and retinal ganglion cells against trypan blue toxicity.
PURPOSE: To determine whether hypothermia of 8 degrees C can protect cultured human retinal pigment epithelial (ARPE-19) cells and rat retinal ganglion cells (RGC-5) against trypan blue (TB) toxicity. DESIGN: Laboratory investigation. METHODS: ARPE-19 cells and RGC-5 were exposed to balanced salt solution as controls, and 0.05% and 0.5% TB at 37 degrees C, and at 8 degrees C for one minute. The percentage of surviving cells was determined by the resazurin test. RESULTS: TB induced a statistically significant decrease in the percentage of ARPE-19 cells surviving at 0.5% TB at 37 degrees C (P < .01). Conversely, TB induced a statistically significant decrease in the percentage of RGC-5 surviving at all conditions except for 0.05% TB at 8 degrees C (0.05% 37 degrees C; P < .05, 0.5% 37 degrees C and 8 degrees C; P < .01). CONCLUSIONS: These results indicate that reducing the temperature to 8 degrees C has a protective effect against the TB toxicity for ARPE-19 cells and RGC-5 in culture.
Animals↗
Molecular and cellular reactions of retinal ganglion cells and retinal glial cells under centrifugal force loading.
PURPOSE: To investigate changes in retinal ganglion cell (RGC) survival and morphology, retinal glial cell effects on RGC survival, and changes in mRNA expression during centrifugal force loading using a newly developed device. METHODS: Changes in RGC survival and morphology were examined when isolated RGCs from 2-day-old rats were loaded with centrifugal force equivalent to 16, 28, or 33 mm Hg. The effects of cocultured retinal glial cells on RGC survival were studied in the presence of centrifugal force equivalent to 16 and 28 mm Hg for 48 hours. The microarray method and real-time polymerase chain reaction confirmed changes in mRNA expression when RGCs and retinal glial cells were loaded with centrifugal force equivalent to 28 mm Hg for 24 hours. RESULTS: The survival of isolated RGCs and the number of neurites were significantly decreased by centrifugal force loading. Conversely, there was no significant change in the survival of isolated retinal glial cells. The survival of cocultured RGCs was significantly better than that of isolated RGCs. In contrast to the numerous changes in the mRNA expression of retinal glial cells subjected to centrifugal force loading, there was no significant change in the mRNA expression of RGCs. CONCLUSIONS: The developed device may have potential for use as an in vitro model of RGC damage. The response to centrifugal force loading varies according to cell type, and the marked changes in the mRNA expression of retinal glial cells may be involved in the improvement of RGC survival.
Animals↗
Retrograde labeling and dissociation of mouse retinal ganglion cells.
Mouse retinal ganglion cells were labeled by retrograde axonal transport of the fluorescent dyes, DAPI and Primulin. The labeled retinae were dispersed by papain treatment and mechanical dissociation. Among the cells in the suspension, the ganglion cells could be unequivocally identified by their intense DAPI/Primulin fluorescence. These results establish that it is possible to label specific neurons in the central nervous system by retrograde transport of fluorescent dyes and to identify the labeled cells after proteolytic dissociation.
Amidines↗