The synaptic ultrastructure in the outer plexiform layer of the catfish retina: A three-dimensional study with hvem and conventional em of golgi-impregnated bipolar and horizontal cells

1986 ◽  
Vol 247 (2) ◽  
pp. 181-199 ◽  
Author(s):  
Soh Hidaka ◽  
Burgess N. Christensen ◽  
Ken-Ichi Naka
Keyword(s):  
Three Dimensional ◽  
Plexiform Layer ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Synaptic Ultrastructure

Roles of aspartate and glutamate in synaptic transmission in rabbit retina. I. Outer plexiform layer

1985 ◽  
Vol 53 (3) ◽  
pp. 699-713 ◽  
Author(s):  
S. A. Bloomfield ◽  
J. E. Dowling
Keyword(s):  
Plexiform Layer ◽  
Second Order ◽  
Bipolar Cells ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Diethyl Ester ◽  
Rabbit Retina ◽  
Lower Vertebrate ◽  
Rods And Cones ◽  
Low Concentrations

Intracellular recordings were obtained from horizontal and bipolar cells of the superfused, isolated retina-eyecup of the rabbit. The putative neurotransmitters aspartate, glutamate, and several analogues were added to the superfusate while the membrane potential and light-responsiveness of the retinal neurons were monitored. Both L-aspartate and L-glutamate mimicked the actions of the endogenous photoreceptor transmitter on horizontal cells, on-bipolar cells, and off-bipolar cells. At applied concentrations of 2.5-20 mM, the actions of L-aspartate and L-glutamate were indistinguishable. D-aspartate potentiated the effects of both L-aspartate and L-glutamate on horizontal cells. This suggests that active uptake systems for these amino acids exist in the outer plexiform layer (OPL) of the rabbit retina. The glutamate analogue kainate produced effects similar to those of aspartate and glutamate on second-order neurons, but at concentrations lower by over two orders of magnitude. The glutamate analogue quisqualate had effects similar to kainate but with much less potency. The aspartate analogue n-methyl DL-aspartate (NMDLA) antagonized the effects of the photoreceptor transmitter on horizontal and off-bipolar cells. This action of NMDLA was only observed at low concentrations (50 microM). In addition, NMDLA could block the effects of exogenously applied kainate. The NMDLA had no clear effects on on-bipolar cells. The glutamate analogue 2-amino-4-phosphonobutyrate reversibly blocked the responses of on-bipolar cells but had no effect on either horizontal or off-bipolar cell responses. This suggests that on-bipolar cells possess a unique synaptic receptor. The aspartate analogue 2-amino-3-phosphonoproprionate did not show this selectivity, suggesting that this unique receptor is a glutamate-preferring receptor. The antagonists alpha-methyl glutamate, alpha-amino adipate, and glutamate diethyl ester all showed only a weak ability to antagonize the actions of the photoreceptor transmitter on second-order neurons. The results of this study indicate that glutamate or a glutamate-like substance is the likely transmitter of rods and cones in the rabbit retina. A comparison of the present findings with those previously obtained in lower vertebrate retinas suggests that the basic pharmacological design of the OPL of all vertebrate retinas is very similar.

Synaptic connexions made by horizontal cells within the outer plexiform layer of the retina of the cat and the rabbit

1974 ◽  
Vol 186 (1085) ◽  
pp. 317-331 ◽  
Keyword(s):  
Horizontal Cell ◽  
Plexiform Layer ◽  
Cell Types ◽  
Bipolar Cells ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Chemical Synapses

Two ultrastructurally distinctive types of horizontal cells are described in the retinae of the cat and the rabbit. Evidence is presented that they have different synaptic connexions in the outer plexiform layer. The majority of the presynaptic structures identified in the outer plexiform layer of the rabbit (as defined on page 320) belong to a neurofilamentous type of horizontal cell. It is suggested that the cat may be the same. No synapses have been identified on to, or from, the second, predominantly neurotubular, type of horizontal cell. No chemical synapses on to, or between, horizontal cells have been found. Thus input of this kind to both types of horizontal cells is as yet only known to be from the photoreceptors. All positively identified postsynaptic processes were the dendrites or perikarya of bipolar cells. Other cell types that are possibly pre- or postsynaptic in the outer plexiform layer are discussed.

Dye coupling in horizontal cells of developing rabbit retina

2000 ◽  
Vol 17 (2) ◽  
pp. 255-262 ◽  
Author(s):  
DIANNA A. JOHNSON ◽  
STEPHEN L. MILLS ◽  
MICHAEL F. HABERECHT ◽  
STEPHEN C. MASSEY
Keyword(s):  
Gap Junctions ◽  
Lucifer Yellow ◽  
Horizontal Cell ◽  
Plexiform Layer ◽  
Cell Types ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Rabbit Retina ◽  
Dye Coupling ◽  
Cell Coupling

In the mature rabbit retina, two classes of horizontal cells, A type and B type, provide lateral inhibition in the outer plexiform layer (OPL) and spatially modify the activation of bipolar cells by photoreceptors. Gap junctions connecting homologous horizontal cells determine the extent to which this inhibitory activity spreads laterally across the OPL. Little is currently known about the expression of gap junctions in horizontal cells during postnatal development or how cell–cell coupling might contribute to subsequent maturational events. We have examined the morphological attributes and coupling properties of developing A and B type horizontal cells in neonatal rabbit retina using intracellular injections of Lucifer Yellow and Neurobiotin. Prelabeling with DAPI permitted the targeting of horizontal cell bodies for intracellular injection in perfused preparations of isolated retina. A and B type horizontal cells were identifiable at birth although their dendritic field sizes had not reached adult proportions and their synaptic contacts in the OPL were minimal. Both cell types exhibited homologous dye coupling at birth. Similar to that seen in the adult, no heterologous coupling was observed, and homologous coupling among A type cells was stronger than that observed among B type cells. The spread of tracer compounds through gap junctions of morphologically immature horizontal cells suggests that ions and other small, bioactive compounds may likewise spread through coupled, horizontal networks to coordinate the subsequent maturational of emerging outer plexiform layer pathways.

Synaptic organization of cone cells in the turtle retina

1971 ◽  
Vol 262 (844) ◽  
pp. 365-381 ◽  
Keyword(s):  
Horizontal Cell ◽  
Plexiform Layer ◽  
Intercellular Junctions ◽  
Bipolar Cells ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Synaptic Organization ◽  
Basal Surface ◽  
Cone Cells ◽  
Cell Processes

The intercellular junctions of cone pedicles in the turtle retina were studied electronmicroscopically in tissue prepared by conventional techniques or impregnated by the method of Golgi. Dendritic branchlets of bipolar cells make specialized contacts with the basal surface of the pedicles. Processes ending laterally to wedge-shaped projections (synaptic ridges) of the pedicles probably belong always to horizontal cells, and make proximal and distal (to the synaptic ridges) junctions with the pedicles. Processes ending opposite the apex of the synaptic ridges are engaged also in two kinds of specialized contacts, termed apical and distal junctions. Basal processes of the cone pedicles make specialized contacts with adjacent pedicles, and with unidentified processes at the outer plexiform layer; their endings abut upon horizontal cell processes lodged within the pedicles of other cone cells.

The interplexiform cell system - I. Synapses of the dopaminergic neurons of the goldfish retina

1978 ◽  
Vol 201 (1142) ◽  
pp. 7-26 ◽  
Keyword(s):  
Bipolar Cell ◽  
Dopaminergic Neurons ◽  
Structural Changes ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Cell System ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Inner Plexiform Layer ◽  
Retinal Neuron

Interplexiform cells are a class of retinal neuron that extends processes widely in both plexiform layers. In goldfish they contain dopamine and readily take up certain biogenic amines. Two of these amines, 6-hydroxyopamine (6-HDA) and 5, 6-dihydroxytryptamine (5,6-DHT), induce fine structural changes in the neurons that accumulate them, allowing the processes of the cells to be recognized by electron microscopy. Typically, the synaptic vesicles within the processes show electron-dense cores. The terminal cytoplasm may also show increased density, as may the cellular and cytoplasmic membranes, presumably an indication of degenerative changes induced by the drugs. 5, 6-DHT gives more readily observable changes than 6-HDA but labels both dopaminergic and indoleamine-accumulating neurons. The terminals of the indoleamine-accumulating terminals were therefore removed by intraocular injections of 5, 7-dihydroxytryptamine (5, 7-DHT) prior to the labelling with 5, 6-DHT. This procedure allowed an analysis of the dopaminergic terminals without interference by the terminals of the indoleamine-accumulating cells. The dopaminergic neurons were found to make synapses of the conventional type. In the outer plexiform layer they contacted both external horizontal cells and bipolar cell dendrites, but not hotoreceptor terminals or intermediate (rod) horizontal cells. No synapses onto the dopaminergic processes were found in the outer plexiform layer despite an extensive search. In the inner plexiform layer the dopaminergic processes were observed to be both pre- and postsynaptic to amacrine cells and their processes. No synaptic contacts between dopaminergic processes and bipolar cell terminals or ganglion cell dendrites were seen. We conclude that the dopaminergic interplexiform cells provide a centri­fugal pathway for information flow in the retina from inner to outer plexiform layer.

scholarly journals Intramembrane organization of specialized contacts in the outer plexiform layer of the retina. A freeze-fracture study in monkeys and rabbits.

1975 ◽  
Vol 65 (1) ◽  
pp. 192-222 ◽  
Author(s):  
E Raviola ◽  
N B Gilula
Keyword(s):  
Gap Junctions ◽  
Internal Structure ◽  
Horizontal Cell ◽  
Freeze Fracture ◽  
Plexiform Layer ◽  
Synaptic Function ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Coated Vesicle ◽  
Synaptic Membranes

Freeze-fracture analysis of the neural connections in the outer plexiform layer of the retina of primates (Macaca mulatta and Macaca arctoides) demonstrates a remarkable diversity in the internal structure of the synaptic membranes. In the invaginating synapses of cone pedicles, the plasma membrane of the photoreceptor ending contains an aggregate of A-face particles, a hexagonal array of synaptic vesicle sites, and rows of coated vesicle sites, which are deployed in sequence from apex to base of the synaptic ridge. The horizontal cell dendrites lack vesicle sites and have two aggregates of intramembrane A-face particles, one at the interface with the apex of the synaptic ridge, the other opposite the tip of the invaginating midget bipolar dendrite. Furthermore, the horizontal cell dendrites are interconnected by a novel type of specialized junction, characterized by: (a) enlarged intercellular cleft, bisected by a dense plate and traversed by uniformly spaced crossbars; (b) symmetrical arrays of B-face particles arranged in parallel rows within the junctional membranes; and (c) a layer of dense material on the cytoplasmic surface of the membranes. The plasmalemma of the invaginating midget bipolar dendrite is unspecialized. At the contact region between the basal surface of cone pedicles and the dendrites of the flat midget and diffuse cone bipolar cells, the pedicle membrane has moderately clustered A-face particles, but no vesicle sites, whereas the adjoining membrane of the bipolar dendrites contains an aggregate of B-face particles. The invaginating synapse of rod spherules differs from that of cone pedicles, because the membrane of the axonal endings of the horizontal cells only has an A-face particle aggregate opposite the apex of the synaptic ridge. Specialized junctions between horizontal cell processes, characterized by symmetrical arrays of intramembrane B-face particles, are also present in the neuropil underlying the photoreceptor endings. Small gap junctions connect the processes of the horizontal cells; other gap junctions probably connect the bipolar cell dendrites which make contact with each cone pedicle. Most of the junctional specializations typical of the primate outer plexiform layer are also found in the rabbit retina. The fact that specialized contacts between different types of neurons interacting in the outer plexiform layer have specific arrangements of intramembrane particles strongly suggests that the internal structure of the synaptic membranes is intimately correlated with synaptic function.

scholarly journals An ethanolic phosphotungstic acid (EPTA) analysis of photoreceptor and synaptic ultrastructure in the guinea pig retina.

1980 ◽  
Vol 28 (2) ◽  
pp. 142-148 ◽  
Author(s):  
K R Fry ◽  
A W Spira
Keyword(s):  
Guinea Pig ◽  
Phosphotungstic Acid ◽  
Plexiform Layer ◽  
Synaptic Cleft ◽  
Basal Bodies ◽  
Inner Plexiform Layer ◽  
Synaptic Terminal ◽  
Presynaptic Membrane ◽  
Synaptic Ultrastructure ◽  
Plexiform Layers

Ethanolic phosphotungstic acid (EPTA) has been used to elucidate the structure of certain organelles contained within retinal cells not clearly discernible using conventional preparations. Both synaptic and nonsynaptic components of the guinea pig neural retina have been analyzed. Within the photoreceptor (PR) cell EPTA-stained components include the connecting cilia, their basal bodies, and the root filament system. Cross-striated fibrillar organelles, similar in appearance to the root filaments, are also observed in the nuclear region, the synaptic terminal and other parts of the PR cell. The possible structural continuity and significance of these structures are discussed. Within retinal synapses of both the inner and outer plexiform layers, ribbons and associated paramembranous specializations are stained. The photoreceptor ribbons have a trialaminar structure with filamentous, tufted borders. Synaptic cleft material and postsynaptic densities are also stained. Bipolar cell synapses in the inner plexiform layer contain stained short ribbons as well as closely associated peg-like densities extending towards the presynaptic membrane.

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