Publications (22) View all
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Article: Synaptic inputs to ON parasol ganglion cells in the primate retina.
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ABSTRACT: In primates, the retinal ganglion cells that project to the magnocellular layers of the lateral geniculate nucleus have distinctive responses to light, and one of these has been identified morphologically as the parasol ganglion cell. To investigate their synaptic connections, we injected parasol cells with Neurobiotin in lightly fixed baboon retinas. The five ON-center cells we analyzed by electron microscopy received approximately 20% of their input from bipolar cells. The major synaptic input to parasol cells was from amacrine cells via conventional synapses and, in this respect, they resembled alpha ganglion cells of the cat retina. We also found the gap junctions between amacrine cells and parasol ganglion cells that had been predicted from tracer-coupling experiments. To identify the presynaptic amacrine cells, ON-center parasol cells were injected with Neurobiotin and Lucifer yellow in living macaque retinas, which were then fixed and labeled by immunofluorescence. Two kinds of amacrine cells were filled with Neurobiotin via gap junctions: a large, polyaxonal cell containing cholecystokinin and a smaller one without cholecystokinin. There were also appositions between cholecystokinin-containing amacrine cell processes and parasol cell dendrites. Cholinergic amacrine cell processes often followed parasol cell dendrites and made extensive contacts. In other mammals, the light responses of polyaxonal amacrine cells like these and cholinergic amacrine cells have been recorded, and the effects of acetylcholine and cholecystokinin on ganglion cells are known. Using this information, we developed a model of parasol cells that accounts for some properties of their light responses.Journal of Neuroscience 01/1997; 16(24):8041-56. · 7.11 Impact Factor -
Article: Bipolar cells specific for blue cones in the macaque retina.
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ABSTRACT: A distinct subpopulation of bipolar cells in macaque monkey retina was labeled with antisera that recognize glycine-extended cholecystokinin precursors. The labeled bipolar cells were found throughout the retina and had dendrites contacting a subpopulation of cone pedicles and axons ramifying in the fifth stratum of the inner plexiform layer. Several lines of evidence indicate that the labeled bipolar cells are a single type despite some variations in their morphology. First, the density of perikarya and their diameters varied continuously as a function of eccentricity. Second, the positions of perikarya within the inner nuclear layer and the level at which the axons branched in the inner plexiform layer were constant at all eccentricities. Bipolar cells with similar morphology have been described previously as "blue cone bipolar cells" (Mariani, 1984b), but there was no direct evidence that this was the case. In this study, we show by light microscopy that labeled bipolar cells have dendrites ending exclusively upon presumptive blue cones labeled by Procion black dye. All blue cones were contacted by labeled bipolar cells, and virtually all bipolar cells contacted blue cones, the only exceptions being in regions where blue cones had been lost. Approximately 20% more labeled bipolar cells than blue cones were found at every eccentricity; thus, connections between blue cones and labeled bipolar cells were not strictly one to one. The mean number of cones presynaptic to each bipolar cell was 1.2, and the mean number of bipolar cells postsynaptic to each cone was 1.8. By an electron microscopic study of labeled bipolar cell dendrites, we determined that they became central elements of ribbon synapses in blue cones. Some of their ribbon synapses were unusual: in one type, a single, large labeled dendrite was postsynaptic to two or more ribbons, while in the other type, ribbons had two or more central elements. The presence of these invaginating contacts and the axonal terminals in the proximal inner plexiform layer suggest that the labeled bipolar cells depolarize to short-wavelength stimuli and function to relay information from blue cones to the inner plexiform layer. There were also other, unlabeled bipolar cell dendrites that received inputs from blue cones at basal junctions and triad-associated flat contacts, which suggests that there are additional types of bipolar cells conveying information from short-wavelength cones in the primate retina.Journal of Neuroscience 05/1992; 12(4):1233-52. · 7.11 Impact Factor -
Article: Photoreceptor-horizontal cell synaptic connections in teleost retina: electron microscopical survey of lucifer yellow-HRP double marking.
Neuroscience Research Supplements 02/1989; 10:S89-100. -
Article: Gap-junctional contacts of luminosity-type horizontal cells in the carp retina: a novel pathway of signal conduction from the cell body to the axon terminal.
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ABSTRACT: L-type horizontal cells (271) of the carp retina were studied with the aid of intracellular injections of Lucifer yellow and horseradish peroxidase (HRP). Coupling among these cells was revealed by passage of the dye out of the injected cell. Thick processes that crossed axons filled with Lucifer yellow also contained the stain. These thick processes appear to be the axon terminals of other horizontal cells. Serial reconstruction of an axon terminal by electron microscopy revealed two groups of elements connected to the axon terminal with putative gap junctions. One large-diameter group was identified as axon terminals of other cells. From the results of the Lucifer dye-coupling experiments, the smaller-diameter elements are thought to be the axons of other horizontal cells. Thus, the axon terminals of carp horizontal cells have putative gap-junctional contacts not only with other axon terminals but also with the axons of other horizontal cells. This newly discovered connection could serve as a pathway for signal transfer between the cell body and the axon terminal of different horizontal cells.The Journal of Comparative Neurology 08/1986; 249(3):404-10. · 3.81 Impact Factor -
Article: Physiological and morphological studies of cone-horizontal cell connections in the turtle retina.
Neuroscience Research Supplements 02/1986; 4:S69-84.
