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

1968 ◽  
Vol 170 (1019) ◽  
pp. 205-228 ◽  
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.

Synaptic microcircuitry of bipolar and amacrine cells with serotonin-like immunoreactivity in the retina of the turtle, Pseudemys scripta elegans

1993 ◽  
Vol 10 (3) ◽  
pp. 455-471 ◽  
Author(s):  
Lawrence B. Hurd ◽  
William D. Eldred
Keyword(s):  
Bipolar Cell ◽  
Amacrine Cell ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Outer Plexiform Layer ◽  
Inner Plexiform Layer ◽  
Synaptic Contacts ◽  
Synaptic Inputs ◽  
Cell Processes

AbstractAlthough serotonin is thought to be a neurotransmitter in a number of retinal systems, much of the precise synaptic connectivity of serotonergic neurons is unknown. To address this issue, we used an antiserum directed against serotonin to label serotonergic bipolar and amacrine cells in the turtle retina. Light-microscopic analysis of labeled amacrine and bipolar cells indicated that both had bistratified dendritic arborizations primarily in stratum 1 and in strata 4/5 of the inner plexiform layer.Ultrastructural analysis of the neurocircuitry of these cells indicated that the processes of labeled bipolar cells in the outer plexiform layer made basal junction contacts with photoreceptor terminals. Only in rare instances did labeled bipolar cells processes invaginate near photoreceptor ribbon synapses. Processes of labeled bipolar cells received both conventional and small ribbon synaptic contacts in the outer plexiform layer. Bipolar cell processes in stratum 1 of the inner plexiform layer synapsed onto either amacrine/amacrine or amacrine/ganglion cell dyads, and made rare ribbon synaptic contacts onto labeled amacrine cell processes. Synaptic inputs to serotonergic bipolar cells in stratum 1 were from unlabeled bipolar and amacrine cells. Bipolar cell contacts in strata 4/5 were similar to those in stratum 1, but were fewer in number and no bipolar cell inputs were seen.Labeled amacrine cell output in both strata was onto other unlabeled amacrine cells and ganglion cells; but synaptic outputs to unlabeled bipolar cells were only seen in strata 4/5. In both strata 1 and 4/5, synaptic inputs to labeled amacrine cells were from both unlabeled amacrine cells and labeled bipolar cells. The serotonergic amacrine cells had many more synaptic interactions in stratum 1 than in strata 4/5 which supports the role of serotonergic bipolar cells in the OFF pathway of retinal processing. Interactions between serotonergic bipolar and amacrine cells may play an important role in visual processing.

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

1991 ◽  
Vol 6 (3) ◽  
pp. 257-269 ◽  
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.

Disruption of transient photoreceptor targeting within the inner plexiform layer following early ablation of cholinergic amacrine cells in the ferret

2001 ◽  
Vol 18 (5) ◽  
pp. 741-751 ◽  
Author(s):  
P.T. JOHNSON ◽  
M.A. RAVEN ◽  
B.E. REESE
Keyword(s):  
Retinal Ganglion Cells ◽  
Amacrine Cell ◽  
Ganglion Cells ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Inner Plexiform Layer ◽  
Retinal Ganglion ◽  
Subcutaneous Injections ◽  
Cell Processes ◽  
Cholinergic Amacrine Cells

Photoreceptors in the ferret's retina have been shown to project transiently to the inner plexiform layer (IPL) prior to their differentiation of an outer segment. On postnatal day 15 (P-15), when this projection achieves maximal density, the photoreceptors projecting into the IPL extend primarily to one of two depths, coincident with the processes of cholinergic amacrine cells. The present study has used an excitotoxic approach employing subcutaneous injections of l-glutamate to ablate these cholinergic amacrine cells on P-7, in order to see whether their elimination alters this targeting of photoreceptor terminals within the IPL. The near-complete elimination of cholinergic amacrine cells at P-15 was confirmed, although the population of retinal ganglion cells was also affected, being depleted by roughly 50%. The rod opsin-immunopositive terminals in such treated ferrets no longer showed a stratified distribution, being found throughout the depth of the IPL, as well as extending into the ganglion cell layer. This effect should not be due to the partial loss of retinal ganglion cells, however, since optic nerve transection at P-2, which eliminates the ganglion cells entirely while leaving the cholinergic amacrine cell population intact, was shown not to affect the stratification pattern of the photoreceptors within the IPL. These results strongly suggest that the targeting of the photoreceptor terminals to discrete strata within the IPL is dependent upon the cholinergic amacrine cell processes.

Nerve Cells and Fibers in the Optic Lobe Cortex of Octopus

1971 ◽  
Vol 29 ◽  
pp. 238-239 ◽  
Author(s):  
Norman M. Case ◽  
E. G. Gray
Keyword(s):  
Optic Nerve ◽  
Synaptic Vesicles ◽  
Granular Layer ◽  
Optic Lobe ◽  
Synaptic Contact ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Nerve Fibers ◽  
Fiber Types ◽  
Basement Layer

Montages of electron micrographs from the outer portion of the cortex of the optic lobe of Octopus are shown. Sheets of dark cytoplasm which originate from glial cells in the outer granular layer form a basement layer separating the outer granular layer from the deeper plexiform layer.Optic nerve fibers from the retina entering the optic lobe around its periphery must pass between the amacrine cells composing the bulk of the outer granular layer. Here they are the darker of the two fiber types that can be identified. Passing through the basement layer they expand into large “carrot” shaped terminal endings easily identified by their dark appearance caused by the extremely high content of synaptic vesicles they contain.Fibers in the neuropil press tightly against and indent the “carrots” and occasionally make synaptic contact with them. Some fibers penetrate deeply into the “carrots” where they branch and terminate in grape-like clusters that show many synaptic contacts with the enveloping bag.

The photoresponses of structurally identified amacrine cells in the turtle retina

1982 ◽  
Vol 214 (1196) ◽  
pp. 403-415 ◽  
Keyword(s):  
Time Course ◽  
Amacrine Cell ◽  
Ganglion Cells ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Homogeneous Distribution ◽  
Inner Plexiform Layer ◽  
Intracellular Recordings ◽  
Cell Processes ◽  
Layer I

Intracellular recordings were obtained from amacrine cells afterwards identified morphologically by horseradish peroxidase injection. There is a correlation between the time course of the photoresponses and the distribution of the cell processes across the inner plexiform layer (i. p. l.). Cells producing the shortest duration, transient ‘on‒off’ photoresponses branched in a single, narrow stratum of the i. p. l. (3‒7 μm across). Transient photoresponses with a longer time course were recorded from cells branching in a thicker stratum of i. p. l. (up to 20 μm), or from bistratified cells. Amacrine cells producing sustained centre-on or centre-off photoresponses were radially diffused across the whole i. p. l.; therefore this type of photoresponse need not be associated with a specific cellular stratification within the i. p. l. It is concluded that the two main functional types of amacrine cell, i. e. transient on‒off and sustained centre-on and centre-off, are subject to different structural organization of inputs than are the homologous physiological types of ganglion cells in this species, in the cat and in the carp. In a summary diagram the observed characteristics of the photoresponses are tentatively explained in term s of a non-homogeneous distribution of bipolar synaptic inputs along amacrine cell processes.

Organization of the primate retina: electron microscopy

1966 ◽  
Vol 166 (1002) ◽  
pp. 80-111 ◽  
Keyword(s):  
Electron Microscopy ◽  
Ganglion Cell ◽  
Bipolar Cell ◽  
Amacrine Cell ◽  
Receptor Cell ◽  
Plexiform Layer ◽  
Cell Physiology ◽  
Inner Plexiform Layer ◽  
Synaptic Contacts ◽  
Cell Processes

The retinae of monkey and man have been studied by electron microscopy to identify cell types, their processes and synaptic contacts. In the inner plexiform layer, the morphological characteristics of the three types of cells (bipolar, ganglion and amacrine) are described and seven synaptic relationships are identified. The bipolar terminals contain ribbons at points of synaptic contact, and, at these points, there are typically two postsynaptic processes, one a ganglion cell dendrite, the other an amacrine cell process. This synaptic arrangement is here termed a dyad. The amacrine cell processes themselves make synaptic contacts with ganglion cell dendrites and somata, other amacrine cell processes, and, most frequently, with the bipolar cell terminals. Often, the amacrine-bipolar contact is adjacent to a bipolar-amacrine junction, forming a reciprocal synaptic arrangement between the bipolar and the amacrine. In the more peripheral retina, large bipolar cell terminals (probably of rod bipolars) are occasionally observed adjacent to the perikarya of the ganglion cells. At these junctions, areas of fusion between the plasma membranes are seen, suggesting that such axosomatic junctions could be electrical. In the outer plexiform layer, synapses have been identified only in the receptor cell bases where receptor cells contact bipolar and horizontal cell processes. Synaptic contacts of the horizontal cells have not been clearly identified, but their strategic terminations in the receptor cell ending are described and interpreted as possibly synaptic. A model of the retina, based on the described anatomy, is presented and correlated with ganglion cell physiology.

Immunocytochemical localization of glycine in the retina of the turtle (Pseudemys scripta)

1989 ◽  
Vol 2 (4) ◽  
pp. 331-338 ◽  
Author(s):  
William D. Eldred ◽  
Kristin Cheung
Keyword(s):  
Ganglion Cell ◽  
Ganglion Cell Layer ◽  
Ganglion Cells ◽  
Cell Layer ◽  
Rabbit Antiserum ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Outer Plexiform Layer ◽  
Inner Plexiform Layer ◽  
Synaptic Interactions

AbstractWe have localized glycine-like immunoreactivity to provide new anatomical detail about glycinergic neurons in the turtle retina. A rabbit antiserum directed against a glycine/albumin conjugate was used with standard fluorescent and avidin-biotin labeling techniques. Some processes in the outer plexiform layer and many processes in the inner plexiform layer, numerous somata in the inner nuclear layer, and isolated somata in the ganglion cell layer were immunoreactive.The vast majority of labeled neurons were amacrine cells. One class of amacrine cells had well-labeled somata near the inner nuclear/inner plexiform layer border, which gave rise to thick primary processes that entered the inner plexiform layer and arborized near the border of strata 1 and 2 and in stratum 3. A second class of glycinergic neurons, consisting of putative interplexiform cells, was unique in that it gave rise to dendritic arborizations in both the outer plexiform layer and the inner plexiform layer. Some of the immunoreactive neurons in the ganglion cell layer were apparently displaced amacrine cells, while others were probably true ganglion cells because they gave rise to labeled axons, and many labeled axons were visible in the ganglion cell axon layer. These results suggested that glycine played an extensive role in the turtle retina, and that it was involved in many diverse synaptic interactions in both the outer plexiform layer and the inner plexiform layer.

Synaptic circuitry of neuropeptide-containing amacrine cells in the retina of the cane toad, Bufo marinus

1995 ◽  
Vol 12 (5) ◽  
pp. 919-927 ◽  
Author(s):  
Bao-Song Zhu ◽  
Ian Gibbins
Keyword(s):  
Ganglion Cell ◽  
Bipolar Cell ◽  
Amacrine Cell ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Bufo Marinus ◽  
Inner Plexiform Layer ◽  
Cane Toad ◽  
Synaptic Inputs ◽  
Cell Processes

AbstractSynaptic connections of amacrine cells with substance P-like or neuropeptide Y-like immunoreactivity (SP-LI or NPY-LI) in the retina of the cane toad, Bufo marinus, were investigated using ultrastructural immunocytochemistry. The perikarya of SP-LI or NPY-LI amacrine cells were located in the innermost row of the inner nuclear layer. The synapses associated with SP-LI amacrine cells were distributed mainly in sublaminae 3 and 4 with about 10% in sublamina 1 of the inner plexiform layer. The synapses formed by NPY-LI amacrine cells were found in sublaminae 1, 2, and 4 with approximately equal frequency. Of a total of 175 SP-LI profiles, 56% were in presynaptic positions and 44% in postsynaptic positions. The synaptic inputs to SP-LI profiles predominantly derived from other unlabeled amacrine cell dendrites, and to a lesser extent, from bipolar cell terminals. The majority of synaptic outputs from SP-LI amacrine cell dendrites were directed onto unlabeled amacrine cell processes. The SP-LI profiles also made synapses onto bipolar cell terminals and formed synapses onto presumed ganglion cell dendrites. Of a total of 200 NPY-LI profiles, 48% were in presynaptic positions and 52% in postsynaptic positions. The profiles of NPY-LI amacrine cells mainly received their synaptic inputs from other unlabeled amacrine cell processes, and to a lesser extent, from bipolar cell terminals. The majority of NPY-LI amacrine cell profiles gave their synaptic outputs onto unlabeled amacrine cell dendrites, and others formed synapses onto presumed ganglion cell processes. These results suggest that these two populations of neuropeptide-containing amacrine cells in the Bufo retina are involved in different synaptic circuits.

Synaptic organization of GABAergic amacrine cells in the salamander retina

2004 ◽  
Vol 21 (6) ◽  
pp. 817-825 ◽  
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.

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.

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