Synaptic vesicle exocytosis in goldfish photoreceptor cells

Matsumura, Miyo; Okinami, Satoshi; Ohkuma, M

doi:10.1007/bf00413147

Cited by 4 publications

(3 citation statements)

References 19 publications

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“…Although the ribbon is typically curved, it maintains a vertical orientation over a troughlike structure called the arciform density. This ribbon-arciform density complex is itself positioned over a specialized depression in the photoreceptor membrane called the synaptic ridge (Dowling and Werblin, 1969;Lasansky, 1973;Raviola and Gilula, 1975;Pierantoni and McCann, 1981;Matsumura et al, 1981;Schaeffer et al, 1982;Townes-Anderson et al, 1985;Rao-Mirotznik et al, 1995). The approximate spatial relationships of these synaptic structures is diagrammed in Fig.…”

Section: Structural Organizationmentioning

confidence: 99%

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: Structural Organizationmentioning

confidence: 99%

Synaptic transmission at retinal ribbon synapses

Heidelberger

Thoreson

Witkovsky

2005

Progress in Retinal and Eye Research

207

231

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“…At the base of the ribbon is a trough-like structure known as the arciform density. The ribbon and arciform density sit above an invaginating depression in the photoreceptor membrane called the synaptic ridge [40,54,55,[58][59][60][61][62][63]. The ribbons of mammalian rods wrap around the synaptic ridge to create a distinctive crescent or horseshoe shape [63].…”

Section: Anatomical Features Of the Photoreceptor Synapsementioning

confidence: 99%

Kinetics of Synaptic Transmission at Ribbon Synapses of Rods and Cones

Thoreson

2007

Mol Neurobiol

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The ribbon synapse is a specialized structure that allows photoreceptors to sustain the continuous release of vesicles for hours upon hours and years upon years but also respond rapidly to momentary changes in illumination. Light responses of cones are faster than those of rods and, mirroring this difference, synaptic transmission from cones is also faster than transmission from rods. This review evaluates the various factors that regulate synaptic kinetics and contribute to kinetic differences between rod and cone synapses. Presynaptically, the release of glutamate-laden synaptic vesicles is regulated by properties of the synaptic proteins involved in exocytosis, influx of calcium through calcium channels, calcium release from intracellular stores, diffusion of calcium to the release site, calcium buffering, and extrusion of calcium from the cytoplasm. The rate of vesicle replenishment also limits the ability of the synapse to follow changes in release. Post-synaptic factors include properties of glutamate receptors, dynamics of glutamate diffusion through the cleft, and glutamate uptake by glutamate transporters. Thus, multiple synaptic mechanisms help to shape the responses of second-order horizontal and bipolar cells. KeywordsPhotoreceptor; Synaptic transmission; Glutamate; Calcium; Vesicles; Retina Vision begins with the transduction of light into membrane potential changes as the result of an enzymatic cascade occurring in the outer segments of rod and cone photoreceptors [1,2]. Light-evoked membrane potential changes are modified by voltage-dependent currents in the inner segment [3] and transmitted to second order bipolar and horizontal cells by changes in release of the neurotransmitter, L-glutamate, from the synaptic terminals of both rods and cones. Because all of the visual information available to downstream retinal neurons must first pass through the photoreceptor synapse, synaptic transmission from photoreceptors has a considerable impact on visual perception. The focus of this review is on mechanisms that shape the kinetics of synaptic transmission at synapses of rods and cones. Additional information on other physiological and anatomical characteristics of photoreceptor ribbon synapses can be found in recent reviews [4][5][6]. Differences in Rod and Cone KineticsRod and cone photoreceptors are tonically depolarized in darkness with membrane potentials of −35 to −45 mV that allow continuous release of the neurotransmitter, L-glutamate. Light onset causes photoreceptors to hyperpolarize by as much as 30 mV, leading to a reduction in

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“…There can be no doubt that at the ribbon synapse, exocytosis (Ball and Dickson, 1983;Matsumura et al, 1981;Schaeffer and Raviola, 1978), followed by endocytosis (Ball and Dickson, 1983;Ripps et al, 1976;Schacher et al, 1976;Schaeffer and Raviola, 19781, takes place. After administration of horseradish peroxidase (HRP), which is taken up by endocytosis, the percentage of ribbon-associated vesicles containing HRP was similar to the overall proportion of labelled vesicles in the photoreceptor terminals (Schacher et al, 1976).…”

Section: Chemistry Of Sr's and Sv'smentioning

confidence: 99%

Plasticity of retinal ribbon synapses

Vollrath

Spiwoks-Becker

1996

Microsc. Res. Tech.

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Ribbon synapses differ from conventional chemical synapses in that they contain, within the cloud of synaptic vesicles (SV's), a specialized synaptic body, most often termed synaptic ribbon (SR). This body assumes various forms. Reconstructions reveal that what appear as rod‐ or ribbon‐like profiles in sections are in fact rectangular or horseshoe‐shaped plates. Moreover, spherical, T‐shaped, table‐shaped, and highly pleomorphic bodies may be present. In mammals, ribbon synapses are present in afferent synapses of photoreceptors, bipolar nerve cells, and hair cells of both the organ of Corti and the vestibular organ. Synaptic ribbons (SR's) are also found in the intrinsic cells of the third eye, the pineal gland, and in the lateral line system. The precise function of SR's is enigmatic. The prevailing concept is that SR's function as conveyor belts to channel SV's to the presynaptic membrane for neurotransmitter release by means of exocytosis. The present article reviews the evidence that speaks for a plasticity of these organelles in the retina and the third eye, as reflected in changes in number, size, shape, location, and grouping pattern. SR plasticity is especially pronounced in the mammalian and submammalian pineal gland and in cones and bipolar cells of teleost fishes. Here, SR number and size wax and wane according to the environmental lighting conditions. In the pineal SR numbers increase at night and decrease during the day. In teleost cones, SR's are in their prime during daytime and decrease or disappear at night, when transmitter release is enhanced. In addition to numerical changes, SR's may also exhibit changes in size, shape, grouping pattern, and location. In the mammalian retina of adults, in contrast to the developing retina, the reported signs of SR plasticity are subtle and not always consistent. They may reflect changes in function or may represent signs of degradation. To distinguish between the two, more detailed studies under selected experimental conditions are required. Probably the strongest evidence for SR plasticity in the mammalian retina is that in hibernating squirrels SR's leave the synaptic site and accumulate in areas as far as 5 μm from the synapse. Changes in shape include the occurrence of club‐shaped SR's and round SR's or synaptic spheres (SS's). SS's may represent a special type of synaptic body, yet belonging to the family of SR's, or may be related to the catabolism of SR's. SR number is regulated by Ca2+ in teleost cones, whereas in the mammalian pineal gland cGMP is involved. An interesting biochemical feature of ribbon synapses is that they lack synapsins. The presently reviewed results suggest to us that SR's do not primarily function as conveyor belts, but are devices to immobilize SV's in inactive ribbon synapses. © 1996 Wiley‐Liss, Inc.

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Synaptic vesicle exocytosis in goldfish photoreceptor cells

Cited by 4 publications

References 19 publications

Synaptic transmission at retinal ribbon synapses

Synaptic transmission at retinal ribbon synapses

Kinetics of Synaptic Transmission at Ribbon Synapses of Rods and Cones

Plasticity of retinal ribbon synapses

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