Structure and function of photoreceptor and second-order cell mosaics in the retina of Xenopus

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Abstract

The structure, physiology, synaptology, and neurochemistry of photoreceptors and second-order (horizontal and bipolar) cells of Xenopus laevis retina is reviewed. Rods represent 53% of the photoreceptors; the majority (97%) are green light-sensitive. Cones belong to large long-wavelength-sensitive (86%), large short-wavelength-sensitive (10%), and miniature ultraviolet wavelength-sensitive (4%) groups. Photoreceptors release glutamate tonically in darkness, hyperpolarize upon light stimulation and their transmitter release decreases. Photoreceptors form ribbon synapses with second-order cells where postsynaptic elements are organized into triads. Their overall adaptational status is regulated by ambient light conditions and set by the extracellular dopamine concentration. The activity of photerectors is under circadian control and is independent of the central body clock. Bipolar cell density is about 6000 cells/mm2. They receive mixed inputs from rods and cones. Some bipolar cell types violate the rule of ON-OFF segregation, giving off terminal branches in both sublayers of the inner plexiform layer. The majority of them contain glutamate, a small fraction is GABA-positive and accumulates serotonin. Luminosity-type horizontal cells are more frequent (∼1000 cells/mm2) than chromaticity cells (∼450 cells/mm2). The dendritic field size of the latter type was threefold bigger than that of the former. Luminosity cells contact all photoreceptor types, whereas chromatic cells receive their inputs from the short-wavelength-sensitive cones and rods. Luminosity cells are involved in generating depolarizing responses in chromatic horizontal cells by red light stimulation which form multiple synapses with blue-light-sensitive cones. Calculations indicate that convergence ratios in Xenopus are similar to those in central retinal regions of mammals, predicting comparable spatial resolution.

Original languageEnglish
Pages (from-to)77-120
Number of pages44
JournalInternational Review of Cytology
Volume210
DOIs
Publication statusPublished - 2001

Fingerprint

Xenopus
Retina
Cones
Luminance
Wavelength
Glutamic Acid
Methyl Green
Mammals
Physiology
gamma-Aminobutyric Acid
Light
Clocks
Transmitters
Dopamine
Serotonin
Vertebrate Photoreceptor Cells
Synapses
Color
Neurochemistry
Darkness

Keywords

  • Bipolar cells
  • Cones
  • Horizontal cells
  • Photoreceptors
  • Retina
  • Rods
  • Synaptology
  • Xenopus

ASJC Scopus subject areas

  • Cell Biology
  • Histology

Cite this

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title = "Structure and function of photoreceptor and second-order cell mosaics in the retina of Xenopus",
abstract = "The structure, physiology, synaptology, and neurochemistry of photoreceptors and second-order (horizontal and bipolar) cells of Xenopus laevis retina is reviewed. Rods represent 53{\%} of the photoreceptors; the majority (97{\%}) are green light-sensitive. Cones belong to large long-wavelength-sensitive (86{\%}), large short-wavelength-sensitive (10{\%}), and miniature ultraviolet wavelength-sensitive (4{\%}) groups. Photoreceptors release glutamate tonically in darkness, hyperpolarize upon light stimulation and their transmitter release decreases. Photoreceptors form ribbon synapses with second-order cells where postsynaptic elements are organized into triads. Their overall adaptational status is regulated by ambient light conditions and set by the extracellular dopamine concentration. The activity of photerectors is under circadian control and is independent of the central body clock. Bipolar cell density is about 6000 cells/mm2. They receive mixed inputs from rods and cones. Some bipolar cell types violate the rule of ON-OFF segregation, giving off terminal branches in both sublayers of the inner plexiform layer. The majority of them contain glutamate, a small fraction is GABA-positive and accumulates serotonin. Luminosity-type horizontal cells are more frequent (∼1000 cells/mm2) than chromaticity cells (∼450 cells/mm2). The dendritic field size of the latter type was threefold bigger than that of the former. Luminosity cells contact all photoreceptor types, whereas chromatic cells receive their inputs from the short-wavelength-sensitive cones and rods. Luminosity cells are involved in generating depolarizing responses in chromatic horizontal cells by red light stimulation which form multiple synapses with blue-light-sensitive cones. Calculations indicate that convergence ratios in Xenopus are similar to those in central retinal regions of mammals, predicting comparable spatial resolution.",
keywords = "Bipolar cells, Cones, Horizontal cells, Photoreceptors, Retina, Rods, Synaptology, Xenopus",
author = "R. G{\'a}briel and M. Wilhelm",
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AU - Gábriel, R.

AU - Wilhelm, M.

PY - 2001

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N2 - The structure, physiology, synaptology, and neurochemistry of photoreceptors and second-order (horizontal and bipolar) cells of Xenopus laevis retina is reviewed. Rods represent 53% of the photoreceptors; the majority (97%) are green light-sensitive. Cones belong to large long-wavelength-sensitive (86%), large short-wavelength-sensitive (10%), and miniature ultraviolet wavelength-sensitive (4%) groups. Photoreceptors release glutamate tonically in darkness, hyperpolarize upon light stimulation and their transmitter release decreases. Photoreceptors form ribbon synapses with second-order cells where postsynaptic elements are organized into triads. Their overall adaptational status is regulated by ambient light conditions and set by the extracellular dopamine concentration. The activity of photerectors is under circadian control and is independent of the central body clock. Bipolar cell density is about 6000 cells/mm2. They receive mixed inputs from rods and cones. Some bipolar cell types violate the rule of ON-OFF segregation, giving off terminal branches in both sublayers of the inner plexiform layer. The majority of them contain glutamate, a small fraction is GABA-positive and accumulates serotonin. Luminosity-type horizontal cells are more frequent (∼1000 cells/mm2) than chromaticity cells (∼450 cells/mm2). The dendritic field size of the latter type was threefold bigger than that of the former. Luminosity cells contact all photoreceptor types, whereas chromatic cells receive their inputs from the short-wavelength-sensitive cones and rods. Luminosity cells are involved in generating depolarizing responses in chromatic horizontal cells by red light stimulation which form multiple synapses with blue-light-sensitive cones. Calculations indicate that convergence ratios in Xenopus are similar to those in central retinal regions of mammals, predicting comparable spatial resolution.

AB - The structure, physiology, synaptology, and neurochemistry of photoreceptors and second-order (horizontal and bipolar) cells of Xenopus laevis retina is reviewed. Rods represent 53% of the photoreceptors; the majority (97%) are green light-sensitive. Cones belong to large long-wavelength-sensitive (86%), large short-wavelength-sensitive (10%), and miniature ultraviolet wavelength-sensitive (4%) groups. Photoreceptors release glutamate tonically in darkness, hyperpolarize upon light stimulation and their transmitter release decreases. Photoreceptors form ribbon synapses with second-order cells where postsynaptic elements are organized into triads. Their overall adaptational status is regulated by ambient light conditions and set by the extracellular dopamine concentration. The activity of photerectors is under circadian control and is independent of the central body clock. Bipolar cell density is about 6000 cells/mm2. They receive mixed inputs from rods and cones. Some bipolar cell types violate the rule of ON-OFF segregation, giving off terminal branches in both sublayers of the inner plexiform layer. The majority of them contain glutamate, a small fraction is GABA-positive and accumulates serotonin. Luminosity-type horizontal cells are more frequent (∼1000 cells/mm2) than chromaticity cells (∼450 cells/mm2). The dendritic field size of the latter type was threefold bigger than that of the former. Luminosity cells contact all photoreceptor types, whereas chromatic cells receive their inputs from the short-wavelength-sensitive cones and rods. Luminosity cells are involved in generating depolarizing responses in chromatic horizontal cells by red light stimulation which form multiple synapses with blue-light-sensitive cones. Calculations indicate that convergence ratios in Xenopus are similar to those in central retinal regions of mammals, predicting comparable spatial resolution.

KW - Bipolar cells

KW - Cones

KW - Horizontal cells

KW - Photoreceptors

KW - Retina

KW - Rods

KW - Synaptology

KW - Xenopus

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JO - International Review of Cell and Molecular Biology

JF - International Review of Cell and Molecular Biology

SN - 1937-6448

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