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Horizontal cells and their photoreceptor connections in the cone-domnated retina of the thee shrew
Friday, Sep 25, 1992 La Palms/A
X ICER Abstracts 821
4 SPECTRAL
OPPONFNCY
IN CONEDRIVEN
CARP HORIZONTAL
TWO LEVELS Peter Gouras Ophthalmology,
CELLS
Lab. of Medical Physics, University of Amsterdam and The Netherlands Ophthalmic Research Institute, Amsterdam, The Netherlands
822 HofuzoNrAL CELLSAND nBFl PHoToREcEpToR CONNEclloNs
5
DOMNAlEDREflNAOFMElREESHREW
MPI f. Himforschung,
Deutschordenstr. 46, W-6000 Frankfurt. Germany The tree shrew retina contains 95% cones and only 5% rods in-its photoreceptor layer. We have studied the cone connections of tree shrew horizontal cells to see whether this cone dominance has lead to a colour-selective wiring. In other ma-Is there is no chromatic selectivity of horizontal cefls. The tree shrew is a dichromat with redand blue-e cones, and the $I pas can be selectively labeled #&Uar & Peichl, JCN 8???&9 Tree shrew tizcntal cells (described b; Mariani, JCN 233: 553 1985) were intracdlulady injected with Lucifer Yellow. After photocon: version the cells were studii lightand electron-microscopically. Tissue containing injected celfs was then immunoreacted with an antibody against retinal S-antigen to specifically label the blue-sensitive cones. The larger A-type horizontal cefis have sparsely branched dendrites; some dendrites end in extensive bushy arborizations (not found in any other mammal). Along the dendrites and on the bushy arborizations, photoreceptor contacts are made by small terminal aggregates. All contacts are exclusively with cones, like in the A-type cells of other mammals. The smaller B-type horizontal cells have a densely branched dendtitic tree with 40-80 terminal aggregates, and a single sparsely branched axOn with only a few terminals. Dendritic terminals exclusively synapse with cones. Both types of horizontal cell contact practically all cones within reach of their dendrites. In particular, we could show directly that they contact both types of cone. Thus there is no chromatic selectivity in tree shrew horizontal cells. [Supported by the DFG: SFB 45/C7]
823
6 COMR
CONNECTMTY
University of Utah, Salt Vienna, Vienna, Austria
OF HUMAN Lake
City,
HORIZONTAL Utah,
USA
CELLS and University
of
Go&i-impregnated horizontal cells of the human retina have been studied by light and electron microscopy to understand their connectivity with the cones overlying their dendritic trees. Since blue conea can be dietinguished from the red and green cones in the human retina on morphological criteria concerning their synaptic pedicles (Ahnelt et al., 1987; 16901, the horizontal cells can be seen to either connect or not, with the blue cones. Thus, HI cells connect to a group of overlying cones and where a blue mne is in the field it geta at moat one or two dendritic terminals. HI1 cells connect to all the overlying cones with a concen&&ion of dendxitic terminals to the blue cones in the field. Their axon terminals connect exclusively to blue cones. HI11 cells connect to all the cones within easy reach of their dendrites with the exception of blue cones. The latter are totally avoided. These findings demonstrate a definite pattern of chromatic selectivity in the horizontal cells of the human retina which could form a feedback system for chromatic opponency at the outer plexiform layer level. Supported by NIH Prevent Blindness.
grant
EY03323
and an award
from Research
OF CONE OPPONENCY IN PRIMATE RETINA Columbia University, Department 630 W. 168 St., New York 10032
of USA
Understanding the role of horizontal cells ip reouires orimate retina is a challenae because it kxtensive recordings from aii varieties of Single cones, horizontal and bipolar cells. There are, however, some clues to their role due to the high degree of specificity in the cone pathways through this retina. This is particularly true for S cones. S cones are restricted to only the tonic (parve) ganglion cell system. These ganglions cells show no spatial opponency (Type II behavior) but striking cone opponency (antagonized by L-M cones). If we assume that antagonism only occurs through horizontal and/or amacrine cells, then we must conclude that there is a horizontal and/or amacrine cell system specific to L-M cones which antagonizes the S cone channels. Because of the phenomenon of transient tritanopia (TT) we have a means of assessing this L-M cone antagonism at the outer retinal layers by the ERG and at the inner retinal (in comparison) by ganglion cell layers recordings. These two methods reveal that TT is present but weak in the ERG but powerful at the level. ganglion cell These results can best be explained by two levels of cone specific opponent interactions in primate retina. One weakly at the outer layers (horizontal) and another stronger at the inner layers (amacrine). Similar assessment of the more complex L and M cone pathways will be made.
Based on their spectral sensitivity, three types of cone driven horizontal cells (Monophasic, Biphasic and Triphasic) can be found in carp retina. Their spectral response characteristics are thought to be generated via feedback from the HC’s to the cones. An elegant cascade model was suggested by Stell (Stell et al., 1975) in which the morphology of the HC dendrites was correlated with the feedforward and feedback properties of the cone/HC contacts. The essence of this model is that the monophasic IX’s receive input from the long wavelength cones and feed back to all cones, that the biphasic HC’s receive input from the middle wavelength sensitive cones and feed back to the middle and short wavelength sensitive cones, and that the triphasic HC’s receive input from the short wavelength sensitive cones only. This model successfully explains the spectral coding of the HC’s. However, it fails to explain the dynamic properties of the HC’s and the behavior of the HC’s under intense stimuli or background illumination. Electrophysiological and morphological data from our group indicate that all HC types receive input from all cone systems and that all HC’s feed back to all cone systems. Further, it was found that the strengths of the feedforward and the feedback pathways between a horizontal cell and a particular spectral cone type are roughly proportional. These findings are the basis for a model for the spectral and dynamic behavior of all cone-driven horizontal cells in carp retina. The model can account for the spectral as well as the dynamic behavior of the HC’s.
INTHECON
824
7
to
S.239
X ICER Abstracts 821
4 SPECTRAL
OPPONFNCY
IN CONEDRIVEN
CARP HORIZONTAL
TWO LEVELS Peter Gouras Ophthalmology,
CELLS
Lab. of Medical Physics, University of Amsterdam and The Netherlands Ophthalmic Research Institute, Amsterdam, The Netherlands
822 HofuzoNrAL CELLSAND nBFl PHoToREcEpToR CONNEclloNs
5
DOMNAlEDREflNAOFMElREESHREW
MPI f. Himforschung,
Deutschordenstr. 46, W-6000 Frankfurt. Germany The tree shrew retina contains 95% cones and only 5% rods in-its photoreceptor layer. We have studied the cone connections of tree shrew horizontal cells to see whether this cone dominance has lead to a colour-selective wiring. In other ma-Is there is no chromatic selectivity of horizontal cefls. The tree shrew is a dichromat with redand blue-e cones, and the $I pas can be selectively labeled #&Uar & Peichl, JCN 8???&9 Tree shrew tizcntal cells (described b; Mariani, JCN 233: 553 1985) were intracdlulady injected with Lucifer Yellow. After photocon: version the cells were studii lightand electron-microscopically. Tissue containing injected celfs was then immunoreacted with an antibody against retinal S-antigen to specifically label the blue-sensitive cones. The larger A-type horizontal cefis have sparsely branched dendrites; some dendrites end in extensive bushy arborizations (not found in any other mammal). Along the dendrites and on the bushy arborizations, photoreceptor contacts are made by small terminal aggregates. All contacts are exclusively with cones, like in the A-type cells of other mammals. The smaller B-type horizontal cells have a densely branched dendtitic tree with 40-80 terminal aggregates, and a single sparsely branched axOn with only a few terminals. Dendritic terminals exclusively synapse with cones. Both types of horizontal cell contact practically all cones within reach of their dendrites. In particular, we could show directly that they contact both types of cone. Thus there is no chromatic selectivity in tree shrew horizontal cells. [Supported by the DFG: SFB 45/C7]
823
6 COMR
CONNECTMTY
University of Utah, Salt Vienna, Vienna, Austria
OF HUMAN Lake
City,
HORIZONTAL Utah,
USA
CELLS and University
of
Go&i-impregnated horizontal cells of the human retina have been studied by light and electron microscopy to understand their connectivity with the cones overlying their dendritic trees. Since blue conea can be dietinguished from the red and green cones in the human retina on morphological criteria concerning their synaptic pedicles (Ahnelt et al., 1987; 16901, the horizontal cells can be seen to either connect or not, with the blue cones. Thus, HI cells connect to a group of overlying cones and where a blue mne is in the field it geta at moat one or two dendritic terminals. HI1 cells connect to all the overlying cones with a concen&&ion of dendxitic terminals to the blue cones in the field. Their axon terminals connect exclusively to blue cones. HI11 cells connect to all the cones within easy reach of their dendrites with the exception of blue cones. The latter are totally avoided. These findings demonstrate a definite pattern of chromatic selectivity in the horizontal cells of the human retina which could form a feedback system for chromatic opponency at the outer plexiform layer level. Supported by NIH Prevent Blindness.
grant
EY03323
and an award
from Research
OF CONE OPPONENCY IN PRIMATE RETINA Columbia University, Department 630 W. 168 St., New York 10032
of USA
Understanding the role of horizontal cells ip reouires orimate retina is a challenae because it kxtensive recordings from aii varieties of Single cones, horizontal and bipolar cells. There are, however, some clues to their role due to the high degree of specificity in the cone pathways through this retina. This is particularly true for S cones. S cones are restricted to only the tonic (parve) ganglion cell system. These ganglions cells show no spatial opponency (Type II behavior) but striking cone opponency (antagonized by L-M cones). If we assume that antagonism only occurs through horizontal and/or amacrine cells, then we must conclude that there is a horizontal and/or amacrine cell system specific to L-M cones which antagonizes the S cone channels. Because of the phenomenon of transient tritanopia (TT) we have a means of assessing this L-M cone antagonism at the outer retinal layers by the ERG and at the inner retinal (in comparison) by ganglion cell layers recordings. These two methods reveal that TT is present but weak in the ERG but powerful at the level. ganglion cell These results can best be explained by two levels of cone specific opponent interactions in primate retina. One weakly at the outer layers (horizontal) and another stronger at the inner layers (amacrine). Similar assessment of the more complex L and M cone pathways will be made.
Based on their spectral sensitivity, three types of cone driven horizontal cells (Monophasic, Biphasic and Triphasic) can be found in carp retina. Their spectral response characteristics are thought to be generated via feedback from the HC’s to the cones. An elegant cascade model was suggested by Stell (Stell et al., 1975) in which the morphology of the HC dendrites was correlated with the feedforward and feedback properties of the cone/HC contacts. The essence of this model is that the monophasic IX’s receive input from the long wavelength cones and feed back to all cones, that the biphasic HC’s receive input from the middle wavelength sensitive cones and feed back to the middle and short wavelength sensitive cones, and that the triphasic HC’s receive input from the short wavelength sensitive cones only. This model successfully explains the spectral coding of the HC’s. However, it fails to explain the dynamic properties of the HC’s and the behavior of the HC’s under intense stimuli or background illumination. Electrophysiological and morphological data from our group indicate that all HC types receive input from all cone systems and that all HC’s feed back to all cone systems. Further, it was found that the strengths of the feedforward and the feedback pathways between a horizontal cell and a particular spectral cone type are roughly proportional. These findings are the basis for a model for the spectral and dynamic behavior of all cone-driven horizontal cells in carp retina. The model can account for the spectral as well as the dynamic behavior of the HC’s.
INTHECON
824
7
to
S.239