Spatial properties of goldfish ganglion cells

We systematically classified goldfish ganglion cells according to their spatial summation properties using the same techniques and criteria used in cat and monkey research. Results show that goldfish ganglion cells can be classified as X-, Y-, or W-like based on their responses to contrast-reversal gratings. Like cat X cells, goldfish X-like cells display linear spatial summation. Goldfish Y-like cells, like cat Y cells, respond with frequency doubling at all spatial positions when the contrast-reversal grating consists of high spatial frequencies. There is also a third class of neurons, which is neither X- nor Y-like; many of these cells' properties are similar to those of the "not-X" cells found in the eel retina. Spatial filtering characteristics were obtained for each cell by drifting sinusoidal gratings of various spatial frequencies and contrasts across the receptive field of the cell at a constant temporal rate. The spatial tuning curves of the cell depend on the temporal parameters of the stimulus; at high drift rates, the tuning curves lose their low spatial frequency attenuation. To explore this phenomenon, temporal contrast response functions were derived from the cells' responses to a spatially uniform field whose luminance varied sinusoidally in time. These functions were obtained for the center, the surround, and the entire receptive field. The results suggest that differences in the cells' spatial filtering across stimulus drift rate are due to changes in the interaction of the center and surround mechanisms; at low temporal frequencies, the center and surround responses are out-of-phase and mutually antagonistic, but at higher temporal rates their responses are in-phase and their interaction actually enhances the cell's responsiveness.     

Contributions of short-wavelength cones to goldfish ganglion cells

Summary There are conflicting reports about the existence and nature of a short-wavelength cone (S-cone) contribution to ganglion cells in the goldfish retina. The present study sought to resolve these discrepancies by examining the S-cone contribution while recording from single ganglion cells in the excised, isolated goldfish retina. The effect of variations in the retinal preparation (gas content and type of background lighting during recording) on the S-cone input was also examined. Cells were classified into one of three types based on the responses at light onset and offset, when responses were driven only by the long-wavelength cone system (L-cones) of the receptive field's center (L+/–(on-excitation/off-inhibition) L–/+, and L+/+). With rare exceptions, the threshold spectral sensitivities of the centers and surrounds of cells that possessed opposite on and off responses (L+/–and L–/+) exhibited S-cone contributions, either prior to and/or during chromatic adaptation of the middle-and long-wavelength cones; the S-cone response was antagonistic to the L-cone input. The L + / + center cells also contained a S-cone input, but it was synergistic to the L-cone input at suprathreshold intensities. These findings were robust across all of the retinal preparations employed. The discrepancies in the previous work were probably due to the incomplete classification of cells because of the use of threshold responses only.This work is based in part on a dissertation submitted by RMM in partial fulfillment of the requirements for a PhD degree from the New School for Social Research, New York, New York     

Germinal cells in the goldfish retina that produce rod photoreceptors

Dividing cells and their progeny in retinae of young goldfish were labeled with [3H]thymidine, and selected cells were reconstructed from serial sections processed for electron microscopic autoradiography. Our goals were to characterize the cells that were identified as rod precursors in previous light microscopic autoradiographical studies and to determine their origin and fate. (In fish the population of rods increases several-fold postembryonically by proliferation of rod precursor cells scattered across the retina). Over 200 labeled cells taken from 11 retinas were examined, and 20 of these were reconstructed in their entirety. Some retinas were examined at short intervals (1 to 48 hr) after [3H]thymidine injection in order to study mitotically active cells, and others were examined after longer intervals (9 or 14 days) to discover the nature of the progeny of labeled dividing cells. Previous evidence from thymidine studies in larval goldfish suggested that proliferating cells destined to produce rods appear first in the inner nuclear layer and later in the outer nuclear layer, where they continue to divide and generate new rods (P.R. Johns, (1982) J. Neurosci. 2, 179). The present results provide morphological evidence in support of the suggestion that rod precursors migrate from inner to outer nuclear layer and, furthermore, show that the precursors are closely associated with, and perhaps guided by, the radial processes of Müller glial cells. Examination of EM autoradiographs of labeled cells at 9 and 14 days after a pulse label with thymidine confirms that the differentiated progeny of dividing precursor cells are exclusively rods. To our knowledge, rod precursors are the first example of a neuronal germinal cell in the vertebrate central nervous system that under normal conditions produces only one type of neuron.     

Enkephalin in the goldfish retina

Enkephalin-like immunoreactive amacrine cells were visualized using the highly sensitive avidin-biotin method. The somas of these cells were situated in the inner nuclear and ganglion cell layers. Enkephalin-stained processes were observed in layers 1, 3, and 5 of the inner plexiform layer. The biosynthesis of sulfur-containing compounds in the goldfish retina was studied by means of a pulse-chase incubation with 35S-methionine. A 35S-labeled compound, which comigrated with authentic Met5-enkephalin on high-performance liquid chromatography (HPLC), was synthesized and was bound competitively by antibodies to enkephalin and by opiate receptors. This compound was tentatively identified as "Met5-enkephalin." The newly synthesized 35S-Met5-enkephalin was released upon depolarization of the retina with a high K+ concentration. This K+-stimulated release was greatly suppressed by 5 mM Co2+, suggesting that the release was Ca2+ dependent. Using a double-label technique, enkephalin immunoreactivity and gamma-aminobutyric acid (GABA) uptake were colocalized to some amacrine cells, whereas others labeled only for enkephalin or GABA. The possible significance of enkephalin-GABA interactions is also discussed.     

Segregation of FMRF amide-immunoreactive efferent fibers from NPY-immunoreactive amacrine cells in goldfish retina

Summary Immunocytochemical studies were conducted on goldfish to determine whether a retinal efferent fiber system, immunoreactive to the tetrapeptide Phe-Met-Arg-Phe-NH₂ (FMRFamide), might contain instead a substance similar to one of the 36-amino acid pancreatic polypeptides, the C-terminus of which is similar to FMRFamide.Our results demonstrate the presence of two separate peptidergic systems, one containing FMRFamide-like, and the other pancreatic polypeptide-like peptides. Antisera to FMRFamide reveal the efferent fibers, whose axons exit the optic nerve and terminate in layer 1 of the inner plexiform layer, as previously described. Antisera to porcine neuropeptide Y, and to avian and bovine pancreatic polypeptides label a sparse population of putative amacrine cell bodies and a dense fiber plexus in layers 1, 3, and 5 of the inner plexiform layer. Based on intensity of staining, this amacrine cell peptide appears to be most similar to neuropeptide-Y.Radioimmunoassay and immunocytochemical staining of retinas in which the efferent fiber peptide was depleted by optic nerve crush confirm in large part the observation that the two peptide systems are distinct. However, there is some cross-recognition of the FMRFamide-like tissue antigen by pancreatic polypeptide antibodies.Double-label studies with antisera to tyrosine hydroxylase and neuropeptide-Y indicate that the pancreatic polypeptide antigen is not co-localized with catecholamines.     

Changes in goldfish retinal ganglion cells during axonal regeneration

Recent work suggests that mammalian retinal ganglion cells may become more like developing ganglion cells in form while regenerating through a peripheral nerve graft. We have injected Lucifer Yellow into regenerating ganglion cells of goldfish to look for similar changes. Within three weeks of injury, we saw dye-coupling to nearby cells, which is a common developmental feature in many species. Dendrites and axons, which in most mature ganglion cells are smooth, became varicose and hairy, like those examined in mammalian development. Secondary axons arose later, not only as side-branches of the primary axon but also from the soma, as in mammalian development and regeneration. Since, in fish, these responses are clearly an intrinsic part of functional regeneration, their equivalence in fish and mammals strengthens the view that a similar regenerative competence may exist in the retinal ganglion cells of all vertebrates.     

Rapid expression of novel proteins in goldfish retina following optic nerve crush

Polyadenylated messenger RNA was isolated from goldfish retinas at various times following unilateral crush of the optic nerve. RNA was translated in a cell-free system and product proteins analyzed by two-dimensional gel electrophoresis and autofluorography. Poly(A)+ mRNA-directed protein synthesis revealed an 8-fold increase in the labeling of polypeptides of about 30 kd Mr and a pI of 5.5 in retinas 2 d following optic nerve crush, compared with control retina mRNA translation products. In vitro labeling of retinal proteins revealed the enhanced synthesis of comparable 30 kd proteins in 2 d post-crush retinas. Evidence presented suggests that this 30 kd protein cluster may correspond to fish 30 kd stress or heat-shock proteins (hsp-30).     

Receptive field mechanisms of ganglion cells in the cat retina

On the basis of anatomical and physiological results of the vertebrate retina, a method is proposed for analysing the respective fields of ganglion cells in the cat retina. In the model, we assume the following: (a) Ganglion cells receive their input from bipolar and/or amacrine cells. (b) The nonlinearity of ganglion cell responses is due to the activities of transient type amacrine cells. The method has been proved to be effective. According to the results of this investigation, the receptive field properties of X type and Y type ganglion cells are heterogeneous. Thus, it may be considered that their receptive fields consist of center and surround mechanisms. The receptive field properties of X-cells are almost linear and the X-cells seem to receive most of their input from bipolar cells. On the other hand, the ones of Y-cells are highly nonlinear. Consequently, it is conceivable that the Y-cells receive their input mainly from transient type amacrine cells.     

Synaptic inputs to the ganglion cells in the tiger salamander retina

The postsynaptic potentials (PSPs) that form the ganglion cell light response were isolated by polarizing the cell membrane with extrinsic currents while stimulating at either the center or surround of the cell's receptive field. The time-course and receptive field properties of the PSPs were correlated with those of the bipolar and amacrine cells. The tiger salamander retina contains four main types of ganglion cell: "on" center, "off" center, "on-off", and a "hybrid" cell that responds transiently to center, but sustainedly, to surround illumination. The results lead to these inferences. The on-ganglion cell receives excitatory synpatic input from the on bipolars and that synapse is "silent" in the dark. The off-ganglion cell receives excitatory synaptic input from the off bipolars with this synapse tonically active in the dark. The on-off and hybrid ganglion cells receive a transient excitatory input with narrow receptive field, not simply correlated with the activity of any presynaptic cell. All cell types receive a broad field transient inhibitory input, which apparently originates in the transient amacrine cells. Thus, most, but not all, ganglion cell responses can be explained in terms of synaptic inputs from bipolar and amacrine cells, integrated at the ganglion cell membrane.     

The nonlinear pathway of Y ganglion cells in the cat retina

Retinal ganglion cells of the Y type in the cat retina produce two different types of response: linear and nonlinear. The nonlinear responses are generated by a separate and independent nonlinear pathway. The functional connectivity in this pathway is analyzed here by comparing the observed second-order frequency responses of Y cells with predictions of a "sandwich model" in which a static nonlinear stage is sandwiched between two linear filters. The model agrees well with the qualitative and quantitative features of the second-order responses. The prefilter in the model may well be the bipolar cells and the nonlinearity and postfilter in the model are probably associated with amacrine cells.     

Local regeneration in the retina of the goldfish

We have studied regeneration of the retina in the goldfish as a model of regenerative neurogenesis in the central nervous system. Using a transsclearal surgical approach, we excised small patches of retina that were replaced over several weeks by regeneration. Lesioned retinas from three groups of animals were studied to characterize, respectively, the qualitative changes of the retina and surrounding tissues during regeneration, the concomitant cellular proliferation, and the quantitative relationship between regenerated and intact retina. The qualitative and quantitative analyses were done on retinas prepared using standard methods for light microscopy. The planimetric density of regenerated and intact retinal neurons was computed in a group of animals in which the normal planimetric density ranged from high to low. Cell proliferation was investigated by making intraocular injections of 5-bromo-2′-deoxyuridine (BUdr) at various survival times to label proliferating cells and processing retinal sections for BUdr immunocytochemistry. The qualitative analysis showed that the surgery created a gap in the existing retina that was replaced with new retina over the subsequent weeks. The BUdr-labeling experiments demonstrated that the excised retina was replaced by regeneration of new neurons. Neuroepithiallike cells clustered on the wound margin and migrated centripetally, appositionally adding new retina to the old. The quantitative analysis showed that the planimetric density of the regenerated neurons approximated that of the intact ones.     

Electronic simulation of ganglion cells of generalized vertebrate cone retina

Electronic simulation of generalized vertebrate cone retina consists of 43x41 grid of red-, green-, and blue-sensitive cones. Each retinal element is simulated by a linear summator in series with a leaky integrator and spatial-temporal properties are developed by spatial organization of cone mosaic into unit hexagons and interplay of antagonistic inputs of differing time courses. Model has full compliments of horizontal and bipolar cells including color- and noncolor coding as well as single- and double-opponent receptive fields for bipolar cells. Electronic simulation also has negative feedback from L-horizontal cells to cones. Ganglion cells are formed by convergence of 7 bipolar cells, either all same and thus homogeneous, or else with a central-DPBC (or HPBC) and 6 surround-HPBCs (or DPBCs) and thus non-homogeneous. Responses of color- and non-color-coded ganglion cells as well as single- and double-opponents are investigated with stationary and moving light spots using white and colored lights. While responses to stationary light spots are predictable from digital models, responses to moving spots are complicated by differing time lags of components involved in total response. Therefore, responses to moving stimuli are more readily simulated by analogue models.     

Development of the mouse retina: emerging morphological diversity of the ganglion cells

The time course and regulatory mechanisms of dendritic development are subjects of intense interest. We approached these problems by investigating dendritic morphology of retinal ganglion cells (RGCs) at four early postnatal stages. The RGCs develop from a diffusely stratified and poorly differentiated group at birth (P0), to 16 distinct, morphologically well-defined subtypes before eye opening (P13). Even before bipolar cells make synaptic contacts with the RGCs (P8), most adultlike RGC subtypes are already present. Similar to previous studies in other mammalian species, our results indicate that the initiation of the RGC morphological maturation is independent of light stimulation and of formation of glutamatergic synapses. This study narrowed down the window of RGCs morphological maturation and highlighted a few early postnatal events as potential factors controlling the developmental process. Because mouse is the most popular mammalian model for genetic manipulation, this study provided a foundation for further exploring regulatory mechanisms of RGC dendritic development.     

Interactions leading to colour opponency in ganglion cells of the turtle retina

In the turtle retina, colour-dependent photoresponses could be recorded intracellularly from ganglion cells receiving only bipolar cell input. Thus, the mechanism for colour discrimination by these ganglion cells (type A) is contained in the outer plexiform layer of the retina and depends on interaction between horizontal and cone cells. Ganglion cells receiving an additional amacrine input (type B) are not influenced by colour, and have about 0.7 logarithmic unit lower absolute sensitivity to peak wavelength than have type A ganglion cells.     

Local regeneration in the retina of the goldfish.

We have studied regeneration of the retina in the goldfish as a model of regenerative neurogenesis in the central nervous system. Using a transscleral surgical approach, we excised small patches of retina that were replaced over several weeks by regeneration. Lesioned retinas from three groups of animals were studied to characterize, respectively, the qualitative changes of the retina and surrounding tissues during regeneration, the concomitant cellular proliferation, and the quantitative relationship between regenerated and intact retina. The qualitative and quantitative analyses were done on retinas prepared using standard methods for light microscopy. The planimetric density of regenerated and intact retinal neurons was computed in a group of animals in which the normal planimetric density ranged from high to low. Cell proliferation was investigated by making intraocular injections of 5-bromo-2'-deoxyuridine (BUdr) at various survival times to label proliferating cells and processing retinal sections for BUdr immunocytochemistry. The qualitative analysis showed that the surgery created a gap in the existing retina that was replaced with new retina over the subsequent weeks. The BUdr-labeling experiments demonstrated that the excised retina was replaced by regeneration of new neurons. Neuroepithial-like cells clustered on the wound margin and migrated centripetally, appositionally adding new retina to the old. The quantitative analysis showed that the planimetric density of the regenerated neurons approximated that of the intact ones.     

Exclusionary dendritic interactions in the retina of the goldfish

The retina of the goldfish grows throughout its life, in part, by the addition of new neurons at the margin. New ganglion cells added at the margin tend not to grow their dendritic arbors into the older, central retina. Hitchcock and Easter (J. Neurosci. 6, 1037-1050 (1986)) proposed that the dendrites of the new cells were prevented from extending centrally within the inner plexiform layer by the dendrites of the previous generations of cells. This proposal was tested by first killing existing ganglion cells with a retrogradely transported neurotoxin (propidium iodide; PI), and then observing the orientation and branching pattern of the dendrites of ganglion cells added subsequently at the margin. Dendrites were stained in retinal wholemounts by intracellular injections of Lucifer yellow. The data showed that cells added subsequent to the PI treatment grew their dendritic arbors preferentially toward central retina consistent with the hypothesis. It is concluded that interactions among adjacent ganglion cells regulates dendritic growth.