Synaptic Transmission between Photoreceptors and Horizontal Cells in the Turtle Retina

Cervetto, Luigi; Piccolino, Marco

doi:10.1126/science.183.4123.417

Cited by 174 publications

(78 citation statements)

References 7 publications

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“…It is thought that photoreceptor terminals release more depolarizing transmitter in the dark than in the light (18)(19)(20)(21) (25). This elevation of cAMP may be indicative of phosphorylase activation, a process in which cAMP plays an important role (26).…”

Section: Resultsmentioning

confidence: 99%

Distribution of 3':5'-cyclic AMP and 3':5'-cyclic GMP in rabbit retina in vivo: selective effects of dark and light adaptation and ischemia.

Orr¹,

Lowry²,

Cohen³

et al. 1976

Proc. Natl. Acad. Sci. U.S.A.

110

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By use of highly sensitive radioimmunoassays, 3':5'-cyclic AMP (cAMP) and 3':5'-cyclic GMP (cGMP) were measured in individual layers of light-and dark-adapted rabbit retinas, and the effects of ischemia were determined. In lightadapted retinas, cGMP levels ranged 50-fold, with over 90% of the total concentrated in the photoreceptor cells. The layer of outer segments contained 95 gmol/kg of dry weight, or three times the concentration present in the remainder of the photoreceptor cell layers. By contrast, levels of cAMP varied only 4-fold; the lowest level (6 gmol/kg of dry weight) was found in the outer segment layer and the highest level (22 ;mol/kg of dry weight) in the inner segment layer of the photoreceptor cells. Dark adaptation elevated cGMP levels only in retinal layers containing photoreceptor cells, and the greatest proportional increase was observed in the synaptic layer of photoreceptor cells. Dark adaptation also caused increases of cAMP that were restricted to the outer plexiform and outer nuclear layers. Ischemia lowered cGMP levels, but only in retinal layers containing photoreceptor cells, and elevated cAMP levels, primarily in the inner layers of the retina. emia was studied. The findings demonstrate that the cyclic nucleotides are discretely localized in retinas and that both light exposure and ischemia produce regionally selective changes in their levels. MATERIALS AND METHODS Tissue Preparation. Randomly bred, 6-month-old pigmented rabbits were obtained locally. Light adaptation consisted of 1 hr of exposure to two 100-watt tungsten bulbs about 25 cm above the rabbits. After the photopic stimulation, the rabbits were killed by decapitation. The eyes were removed, and after various ischemic periods in room light, were quickly frozen in liquid N2 cooled to its freezing point by partial evaporation under reduced pressure. Consequently, the liquid N2 does not boil when the eyes are immersed, and freezing is quicker. Dark adaptation consisted of an overnight period in cages wrapped with black cloth and placed in a completely dark room. After decapitation in this room, the dark-adapted eyes were dissected free with the aid of an infrared light source and an infrared image converter, and after various periods, were frozen in the dark as above. Under the most ideal conditions it required 1 min (46-69 sec) to remove and freeze either the light-or dark-adapted eyes. All eyes were stored at -70°until sectioned. Tangential sections (6 ,m) of the retinas were cut at -20°and dried at -400 under reduced pressure. Sections were taken from the paracentral regions of the retina, and care was taken to avoid that portion underlying the myelinated fiber bundle. Paracentral areas of rabbit retina are poorly vacularized (9). Samples (0.03-0.9 ,g dry weight) were dissected from the individual retinal layers and weighed on a quartz-fiber balance (10). Stained, undissected retinal sections were used to help identify individual layers.Assay of cGMP and cAMP. The procedures used for extraction and radioimmunoas...

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Section: Resultsmentioning

confidence: 99%

Distribution of 3':5'-cyclic AMP and 3':5'-cyclic GMP in rabbit retina in vivo: selective effects of dark and light adaptation and ischemia.

Orr¹,

Lowry²,

Cohen³

et al. 1976

Proc. Natl. Acad. Sci. U.S.A.

110

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“…However, our studies provide no information about the time course or voltage dependence of Ca inactivation. This matter is of some interest, since there is pharmacological and anatomical evidence that receptors release synaptic transmitter continuously in darkness (Dowling & Ripps, 1973;Cervetto & Piccolino, 1974;Ca2+ SPIKES IN RODS Dacheux & Miller, 1976;Kaneko & Shimazaki, 1976;Ripps, Shakib & MacDonald, 1976). This presumably could not occur if the receptor Ca conductance were completely inactivated at the dark resting membrane potential.…”

Section: Discussionmentioning

confidence: 99%

Calcium spikes in toad rods.

Fain¹,

Gerschenfeld²,

Quandt³

1980

The Journal of Physiology

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SUMMARY1. When the retina of the toad, Bufo marines, was superfused with 6-12 mMtetraethylammonium chloride (TEA), intracellular recordings from rods showed large, depolarizing regenerative potentials. For brief exposures to TEA, these potentials occurred during the recovery phase of the light responses; whereas, during longer exposures, they were spontaneous in darkness but suppressed during illumination. Similar regenerative potentials were observed during perfusion with 3-10 mM-4-aminopyridine and 1-2 mM-BaCl2.2. 4. The regenerative potentials were blocked by 25 /SM-Cd2+, 50-100 /LM-Co2+j 5mM-Mg2+, and 100 ,tM-D-600. They were unaffected by 2 /LM-TTX or 2-5 mM-Na aspartate.5. In Ringer containing 12 mM-TEA, large anode break responses could be recorded from rods at the termination of inward current pulses. These anode break responses were also suppressed by Co2+ and unaffected by TTX or Na aspartame.6. We conclude that the membrane of toad rods contains a conductance normally selective for Ca2+, which is activated by depolarization. In normal Ringer, the inward current through this conductance produces little effect, since it is balanced by a large outward current, probably carried by K+. TEA and other agents appear to block this outward current, permitting the Ca2+ current to become regenerative.

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“…Although the photoreceptor transmitter appears to be released maximally in the dark, and serves to depolarize the horizontal cells (Trifonov, 1968;Dowling & Ripps, 1973;Cervetto & Piccolino, 1974), the specific effect of the transmitter upon the subsynaptic membrane remains unknown. Studies to elucidate the synaptic mechanism are difficult because horizontal cells, particularly in fish, receive an additional input from neighbouring horizontal cells.…”

Section: Introductionmentioning

confidence: 99%

Synaptic transmission to the horizontal cells in the retina of the larval tiger salamander.

Marshall¹,

Werblin²

1978

The Journal of Physiology

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SUMMARY1. The receptive field diameter for most horizontal cells far exceeds the lateral spread of processes for any cell. Therefore horizontal cells probably receive synaptic input from neighbours as well as from the photoreceptors. The electrical effects of these two synaptic inputs were studied.2. We have characterized the electrical properties of the horizontal cell inputs by determining the current-voltage curves in dark and light. These curves were compared with those obtained in the presence of blockers of synaptic transmission, and during the application of some putative transmitter agents.3. The light response of the cells with narrow receptive fields, near 0 5 mm in diameter, was associated with a conductance decrease. The input resistance was typically 25 MQ, and increased to about 33 MK2 during the light response. The current-voltage curves in light and dark intersected near + 50 mV. The currentvoltage curve in the presence of C02+ or Mg2+ was nearly identical to the curve in the light.4. The putative transmitter substances glutamate, aspartate and GABA depolarized the cells by increasing conductance. Current-voltage curves measured in the presence of these substances intersected the dark and light curves at + 50 mV, the same level at which the dark and light curves intersect.5. The light response of cells with broad receptive fields, between 1.0 and 2*0 mm, showed little or no change in conductance associated with the light response. The input resistance was near 20 MQ, and the current-voltage curves intersected at an extrapolated potential level near 200 mV.6. In the presence of ACh, electrical properties of the broad field cells reverted to those of the narrow field cells: the receptive field was reduced to 0 5 mm, the input resistance increased, and the current-voltage curves intersected near +50 mV. Thus ACh appeared to interrupt synaptic input from neighbouring horizontal cells.7. The results confirm the suggestion that horizontal cells receive a tonic excitatory input from the photoreceptors which is decreased by light. They show that horizontal cells receive an additional input from their neighbours, not associated with a measurable conductance change. The input from neighbours is selectively inter-* Present address:

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Synaptic Transmission between Photoreceptors and Horizontal Cells in the Turtle Retina

Cited by 174 publications

References 7 publications

Distribution of 3':5'-cyclic AMP and 3':5'-cyclic GMP in rabbit retina in vivo: selective effects of dark and light adaptation and ischemia.

Distribution of 3':5'-cyclic AMP and 3':5'-cyclic GMP in rabbit retina in vivo: selective effects of dark and light adaptation and ischemia.

Calcium spikes in toad rods.

Synaptic transmission to the horizontal cells in the retina of the larval tiger salamander.

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