An analysis of transmission from cones to hyperpolarizing bipolar cells in the retina of the turtle.

Ashmore, Jonathan; Copenhagen, David R.

doi:10.1113/jphysiol.1983.sp014781

Cited by 69 publications

(62 citation statements)

References 36 publications

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“…In contrast, the rate needed to sustain responses using a quantal release model was determined to be only 100 v/ribbon/s. Although bipolar cells and photoreceptors are capable of releasing vesicles at the prodigious rates predicted by the cleft-integration mode Kreft et al, 2003), evidence discussed earlier suggests that tonic release in darkness involves much more modest rates of 18-400 vesicles/ribbon/s (Rieke and Schwartz, 1996;Ashmore and Copenhagen, 1983;, consistent with a quantal release model.…”

Section: Do Post-synaptic Responses Conform To the Quantal Hypothesis?supporting

confidence: 55%

“…Again, assuming 125-235 docked vesicles, this value collapses to 2-3 vesicles/s/release site. Release from cone terminals in the turtle retina at the dark resting potential has been estimated from fluctuation analysis to be 20-80 vesicle/ribbon/s (Ashmore and Copenhagen, 1983). Turtle cone ribbons have similar dimensions to salamander rod ribbons and tether similar number of vesicles (Pierantoni and McCann, 1981).…”

Section: Vesicle Pools and Versatility Of Ribbon Synapsesmentioning

confidence: 99%

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Synaptic transmission at retinal ribbon synapses

Heidelberger

Thoreson

Witkovsky

2005

Progress in Retinal and Eye Research

207

231

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The molecular organization of ribbon synapses in photoreceptors and ON bipolar cells is reviewed in relation to the process of neurotransmitter release. The interactions between ribbon synapseassociated proteins, synaptic vesicle fusion machinery and the voltage-gated calcium channels that gate transmitter release at ribbon synapses are discussed in relation to the process of synaptic vesicle exocytosis. We describe structural and mechanistic specializations that permit the ON bipolar cell to release transmitter at a much higher rate than the photoreceptor does, under in vivo conditions. We also consider the modulation of exocytosis at photoreceptor synapses, with an emphasis on the regulation of calcium channels.

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Section: Do Post-synaptic Responses Conform To the Quantal Hypothesis?supporting

confidence: 55%

Section: Vesicle Pools and Versatility Of Ribbon Synapsesmentioning

confidence: 99%

Synaptic transmission at retinal ribbon synapses

Heidelberger

Thoreson

Witkovsky

2005

Progress in Retinal and Eye Research

207

231

View full text Add to dashboard Cite

show abstract

“…The bridge on the amplifier was balanced before penetrating a cell. In addition, voltage responses were corrected for any unbalanced increase in electrode resistance after penetration by subtracting an I-V curve obtained immediately after the electrode was withdrawn from the cell (Ashmore and Copenhagen, 1983).…”

Section: Methodsmentioning

confidence: 99%

Different Circuits for ON and OFF Retinal Ganglion Cells Cause Different Contrast Sensitivities

Zaghloul¹,

Boahen

Demb³

2003

J. Neurosci.

214

309

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The theory of "parallel pathways" predicts that, except for a sign reversal, ON and OFF ganglion cells are driven by a similar presynaptic circuit. To test this hypothesis, we measured synaptic inputs to ON and OFF cells as reflected in the subthreshold membrane potential. We made intracellular recordings from brisk-transient (Y) cells in the in vitro guinea pig retina and show that ON and OFF cells in fact express significant asymmetries in their synaptic inputs. An ON cell receives relatively linear input that modulates a single excitatory conductance; whereas an OFF cell receives rectified input that modulates both inhibitory and excitatory conductances. The ON pathway, blocked by L-AP-4, tonically inhibits an OFF cell at mean luminance and phasically inhibits an OFF cell during a light increment. Our results suggest that basal glutamate release is high at ON but not OFF bipolar terminals, and inhibition between pathways is unidirectional: ON 3 OFF. These circuit asymmetries explain asymmetric contrast sensitivity observed in spiking behavior.

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“…However, at the lower scotopic intensities, where photons are sparse in time and space, the dominant source of noise is not quantum fluctuation, but rather the continuous dark noise in the rod outer segment (Baylor et al, 1980). In this case, pooling many rods would cause little increase in rod signal because photons are sparse, whereas the noise would increase as the square root of the number of rods converging, and would overpower the fragile rod signal (Ashmore and Copenhagen, 1983;Baylor et al, 1984;Schwartz, 1977). This consideration has led to the suggestion that the quanta1 signal in a mammalian rod must be subjected to some form of thresholding or filtering before it is pooled with the signals of other rods (Baylor et al, 1984;Hagins et al, 1970).…”

Section: Modulation Of the Gap Junctionsmentioning

confidence: 99%

Microcircuitry of the dark-adapted cat retina: functional architecture of the rod-cone network

Smith¹,

Freed²,

Sterling³

1986

J. Neurosci.

230

186

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The structure of the rod-cone network in the area centralis of cat retina was studied by reconstruction from serial electron micrographs. About 48 rods converge on each cone via gap junctions between the rod spherules and the basal processes of the cone pedicle. One rod diverges to 2.4 cones through these gap junctions, and each cone connects to 8 other cones, also through gap junctions. A static cable model of this network showed that at mesopic intensities, when all rods converging on a cone pedicle are continuously active, the collective rod signal would be efficiently conveyed to the pedicle. At scotopic intensities sufficiently low for only one of the converging rods to receive a single photon within its integration time, the quantal rod signal would be poorly transmitted to the cone pedicle. This is because the tiny signal would be dissipated by the large network into which the individual rod diverges. Under this condition, the rod signal would also be poorly conveyed to the rod spherule. If, however, the rods are electrically disconnected from the network, the quantal signal would be efficiently conveyed to the rod spherule. This analysis suggests that the rod signal is conveyed at mesopic intensities by the cone bipolar pathway and, at scotopic intensities, by the rod bipolar pathway, in accordance with the results of Nelson (1977, 1982; Nelson and Kolb, 1985).

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An analysis of transmission from cones to hyperpolarizing bipolar cells in the retina of the turtle.

Cited by 69 publications

References 36 publications

Synaptic transmission at retinal ribbon synapses

Synaptic transmission at retinal ribbon synapses

Different Circuits for ON and OFF Retinal Ganglion Cells Cause Different Contrast Sensitivities

Microcircuitry of the dark-adapted cat retina: functional architecture of the rod-cone network

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