Synaptic organization of the inner plexiform layer in the retina of the tiger salamander

AbstractVertical Slices of postnatal day 6 (P6) rat retina were cut and cultured using the roller-tube technique. The organotypic differentiation during a culture period of up to 30 days has been described in a previous study (Feigenspan et al., 1993a). Here we concentrated on the synaptic organization in the retinal slice culture. Electron microscopy revealed the presence of ribbon synapses in the outer plexiform layer and conventional and ribbon syanpses in the inner plexiform layer. Immunofluroscence with antibodies that recognize specific subunits of GABAA or glycine receptors revealed a punctuate distribution of the receptors. They were aggregated in “hot spots” that correspond to a concentration of receptors at postsynaptic sites. Different isoforms of GABAA and glycine receptors occured in the slice cultures. The experiments show that there is a differentiation of synapses and a diversity of transmitter receptors in the slice cultures that is comparable to the in vivo retina.

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Localization of GABAA receptor subtypes in the tiger salamander retina

Visual Neuroscience ◽

10.1017/s0952523800006490 ◽

1992 ◽

Vol 8 (1) ◽

pp. 57-64 ◽

Cited By ~ 17

Author(s):

Chen-YU Yang ◽

Zhen-Shi Lin ◽

Stephen Yazulla

Keyword(s):

Binding Sites ◽

Benzodiazepine Receptors ◽

Plexiform Layer ◽

Receptor Subtypes ◽

Tiger Salamander ◽

Inner Plexiform Layer ◽

Inner Retina ◽

Site Specific ◽

Gabaa Receptor Subtypes ◽

Muscimol Binding

AbstractDry autoradiography was used to determine the distribution of GABAA binding sites in tiger salamander retina. High-affinity binding of [3H]-flunitrazepam ([3H]-FNZ) was used to localize benzodiazepine receptors (BZR) and [3H]-muscimol was used to localize the GABAA recognition site. Specific [3H]-FNZ binding was present only in the inner retina, primarily in the inner plexiform layer (IPL). Co-incubation with GABA enhanced [3H]-FNZ binding by 20–50%. [3H]-muscimol binding was found throughout the IPL and in the outer plexiform layer (OPL). Mouse monoclonal antibodies 62–3G1 and BD-17, that recognize the GABAAβ2, β3 polypeptides, and BD-24, that recognizes the GABAA α1, polypeptide, did not label either the OPL or IPL, despite numerous variations in the fixation and immunoprocessing methods. GABAA receptor location, as revealed by [3H]-muscimol binding, matches the distribution of presumed GABAergic terminals in the OPL and IPL. We suggest that there are at least two subtypes of GABAA receptor in the tiger salamander retina: one type is present only in the inner retina, primarily in the IPL and is functionally coupled to BZRs; the other type is located in the OPL and is not coupled to the BZRs. Furthermore, GABAA receptors in the tiger salamander retina appear to be of a different epitope than GABAA receptors in numerous other preparations that are recognized by mAbs 62–3G1, BD-17, and BD-24.

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Synaptic organization of two types of amacrine cells with CRF-like immunoreactivity in the turtle retina

Visual Neuroscience ◽

10.1017/s095252380000626x ◽

1991 ◽

Vol 6 (3) ◽

pp. 257-269 ◽

Cited By ~ 14

Author(s):

Douglas E. Williamson ◽

William D. Eldred

Keyword(s):

B Cells ◽

Plexiform Layer ◽

Amacrine Cells ◽

Type A ◽

Inner Plexiform Layer ◽

Synaptic Organization ◽

Type B ◽

Synaptic Contacts ◽

A Cells ◽

Visual Streak

AbstractThe ultrastructural features and synaptic contacts of two amacrine cell types with corticotropin-releasing factor-like immunoreactivity in the turtle retina were examined using electron immunocytochemistry. Type A cells were found only in the visual streak and had elongated dendritic arborizations that ran parallel to the visual streak. These cells arborized primarily in stratum 1 and near the border of strata 2 and 3 of the inner plexiform layer, with some processes extending into stratum 5. Type B cells were found only ventral to the visual streak and arborized primarily in a wide band in strata 4 and 5, with sparse dendritic arborizations in stratum 1.There was a diffuse cytoplasmic reaction product within each cell type; however, large labeled vesicles were rarely observed. Type A amacrine cells received many conventional synaptic contacts from amacrine cells in stratum 1 and at the border of strata 2 and 3, but only a small number of contacts in stratum 5. Bipolar synaptic contacts onto type A amacrine cells were observed in strata 1 and at the border of strata 2 and 3. The only positively identified synaptic outputs of type A cells were conventional synapses onto amacrine cells in strata 1 and at the border of 2 and 3. Type B amacrine cells received synaptic contacts from amacrine cells in strata 1 and 5, and bipolar cell synaptic input in stratum 5. They made conventional synapses onto amacrine cells in strata 1 and 5, and onto bipolar cells in stratum 5. We also found conventional synaptic contacts between unlabeled amacrine cells and type B amacrine cells outside of the primary layers of stratification. In addition, there were specialized junctions observed between type A cell profiles in stratum 1 and between type B cell profiles in stratum 5. The unique regional distributions of the type A and B cells, as well as their differences in synaptic connectivity, suggested that these amacrine cells play distinct physiological roles although they contain the same neuropeptide.

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Synaptic organization of the frog retina: an electron microscopic analysis comparing the retinas of frogs and primates

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1968.0034 ◽

1968 ◽

Vol 170 (1019) ◽

pp. 205-228 ◽

Cited By ~ 132

Keyword(s):

Synaptic Vesicles ◽

Synaptic Contact ◽

Plexiform Layer ◽

Amacrine Cells ◽

Outer Plexiform Layer ◽

Inner Plexiform Layer ◽

Synaptic Organization ◽

Synaptic Contacts ◽

Frog Retina ◽

Cell Processes

The synaptic contacts in the inner and outer plexiform layers of the frog retina have been identified and studied by electron microscopy. In the inner plexiform layer, two types of synaptic contact were recognized. One type, believed to be the synaptic contact of the bipolar terminals, is characterized by a synaptic ribbon in the presynaptic cytoplasm. At such ribbon contacts, there are ordinarily two postsynaptic elements, both of which usually contain numerous synaptic vesicles and appear morphologically identical. The second type of synaptic contact in the inner plexiform layer has a more conventional morphology and is observed very much more frequently than are the ribbon contacts. It is characterized by a dense aggregation of synaptic vesicles clustered close to the presynaptic membrane and is thought to be the synaptic contact of the amacrine processes. The conventional synapses are presynaptic to ribbon-containing processes, ganglion cell dendrites, and other amacrine cell processes. Reciprocal contacts between processes making ribbon synapses, and processes making conventional synapses are often observed. Serial synapses between morphologically identical processes, presumably amacrine processes, are frequently seen; and up to four synapses in series between five adjacent processes have been observed. These findings suggest that in the inner plexiform layer of the frog: (1) bipolar terminals synapse primarily with amacrine processes; (2) amacrine processes synapse extensively with the processes of other amacrine cells; and (3) ganglion cells are driven primarily by the amacrine cells. In the outer plexiform layer, processes penetrate into invaginations in the bases of the receptor terminals and lie in close proximity to the synaptic ribbons of the terminals, where the processes presumably receive synaptic input from the receptors. Elsewhere in the outer plexiform layer, knob-like processes, probably from horizontal cells, make conventional synaptic contacts with other horizontal cell processes and probably with bipolar dendrites.

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Synaptic organization of GABAergic amacrine cells in the salamander retina

Visual Neuroscience ◽

10.1017/s0952523804216029 ◽

2004 ◽

Vol 21 (6) ◽

pp. 817-825 ◽

Cited By ~ 6

Author(s):

JUN ZHANG ◽

HO-HWA WANG ◽

CHEN-YU YANG

Keyword(s):

Amacrine Cell ◽

Plexiform Layer ◽

Amacrine Cells ◽

Bipolar Cells ◽

Inner Plexiform Layer ◽

Synaptic Organization ◽

Proximal Margin ◽

Functional Roles ◽

Small Peak ◽

Immuno Electron Microscopy

The synaptic organization of GABA-immunoreactive (GABA-IR) amacrine cells in the inner plexiform layer (IPL) of salamander retina was studied with the use of postembedding immuno-electron microscopy. A total of 457 GABA-IR amacrine synapses, with identified postsynaptic elements, were analyzed on photomontages of electron micrographs covering 3,618 μm2 of the IPL. GABA-IR amacrine synapses were distributed throughout the IPL, with a small peak at the proximal margin of sublamina a. The majority of the output targets (81%) were GABA(−) neurons. Most of the contacts were simple synapses with one postsynaptic element identified as a process of an amacrine cell (55%), bipolar cell (19%) or ganglion cell (26%), and serial synapses were very rare. Of the 89 postsynaptic bipolar terminals, 63% participated in a reciprocal feedback synapse with the same presynaptic GABA-IR amacrine profile. There appeared to be no preference between GABA-IR amacrine contacts with rod- or cone-dominated bipolar cells (9.1% vs. 8.9%) or in the total number of amacrine synapses in sublaminas a and b (52% vs. 47%). The preponderance of amacrine cell input to bipolar cells in the OFF layer was derived from GABA-IR cells. These findings provide ultrastructural support to the existing physiological studies regarding the functional roles of the GABAergic amacrine cells in this species. Our results have added to the data base demonstrating that, in contrast to mammals, GABA-IR amacrine cells in amphibians and other nonmammals contact other amacrine cells more frequently, suggesting greater involvement of GABAergic amacrine cells in modulating lateral inhibitory pathways.

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Synaptic organization of the inner plexiform layer of the retina of Xenopus laevis

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1978.0032 ◽

1978 ◽

Vol 201 (1142) ◽

pp. 57-72 ◽

Cited By ~ 6

Keyword(s):

Xenopus Laevis ◽

South African ◽

Plexiform Layer ◽

Uranyl Acetate ◽

Inner Plexiform Layer ◽

Lead Citrate ◽

Synaptic Organization ◽

Ribbon Synapses ◽

Layer I ◽

Clawed Frog

The inner plexiform layer (i. p. l.) of the retina of the South African clawed frog, Xenopus laevis , was studied by electron microscopy. Photomicrographs of single sections revealed synaptic morphologies comparable to those in other vertebrate retinae. In a partial serial reconstruction of a bipolar terminal, however, some unusual arrangements were found. The bipolar terminal made some synapses that at first examination appeared much like conventional synapses, but subsequent sections always revealed an extremely small ribbon. Many of the ribbon synapses were found to contact more than two postsynaptic processes; up to six processes postsynaptic to one ribbon contact were seen. A reciprocal synapse was not evident at each ribbon synapse. Montages of the entire width of the inner plexiform layer were constructed from sections cut from four different locations across the retina. The numbers of conventional and ribbon synapses per unit volume of tissue were determined. The synaptic densities found in Xenopus were much lower than those reported for other frogs. Differences in synaptic densities from the four locations were found to be statistically insignificant. The overall amacrine/bipolar synapse ratio was 6.8/1. The synaptic densities in the inner plexiform layer did not change when the tissue was stained with lead citrate alone rather than with uranyl acetate and lead citrate. The functional significance of the morphological and quantitative synaptic arrangements in Xenopus i. p. l. is discussed, and the synaptic organization is compared to that of other amphibia and vertebrates.

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Synaptic organization of dopaminergic interplexiform cells in the goldfish retina

Visual Neuroscience ◽

10.1017/s0952523800000997 ◽

1988 ◽

Vol 1 (1) ◽

pp. 13-29 ◽

Cited By ~ 93

Author(s):

Stephen Yazulla ◽

Charles L. Zucker

Keyword(s):

Ganglion Cell ◽

Plexiform Layer ◽

Amacrine Cells ◽

Bipolar Cells ◽

Gaba Uptake ◽

Inner Plexiform Layer ◽

Synaptic Organization ◽

Input And Output ◽

Chemical Synapses ◽

Goldfish Retina

AbstractThe synaptic organization of dopaminergic interplexiform cells (DA-IPC) in the goldfish retina was studied by a combined double-label electron-microscopical (EM) immunocytochemical/autoradiographical study. DA-IPCs were labeled with antisera against tyrosine hydroxylase. The possibility of synaptic contact with GABAergic amacrine cells in the proximal inner plexiform layer (IPL) was studied by using 3H-GABA uptake. Most synaptic input and output from DA-IPC processes involved amacrine cell processes. In addition, synaptic interactions were observed between DA-IPC processes and bipolar cell terminals, other DA-IPC processes, very small dendrites in the IPL, ganglion cell and optic fiber layers (OFL), and cell bodies in the ganglion cell layer (GCL). Input and output synapses with GABAergic amacrine processes also were observed. Two-thirds of the DA-IPC boutons in the proximal IPL were involved in “junctional appositions,” that is, the junctions appeared to be specialized but they were different than classical chemical synapses. The synaptic organization of DA-IPCs in the goldfish IPL appears to be far more complex than previously thought. Although earlier studies have attempted to explain the action of dopamine in terms of interaction only with amacrine cells, the present study shows that effects involving bipolar cells, other DA-IPCs, unidentified processes and cell bodies in the GCL and OFL must be considered as well.

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