The Morphological Organization of the Vertebrate Retina

Stell, William K.

doi:10.1007/978-3-642-65340-7_4

Cited by 96 publications

(45 citation statements)

References 246 publications

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“…Since, in rods, the slow K+ and Ca2+ currents have approximately the same time course of decay after the termination of the current pulse, it is possible that the two are interrelated. That is, the K+ conductance increase may be gated by the entry of Ca2+, as has been proposed for a variety of other cell types (Meech, 1974;Meech & Standen, 1975;Heyer & Lux, t976;Thomas & Gorman, 1977;Krnjevic & Lisiewicz, 1972;Barrett & Barrett, 1976;Clustin et al 1975 (Stell, 1972). There is good reason to believe that the mechanism of transmitter release in rods may be similar to that in other presynaptic neurones.…”

Section: Afterpotentials and Slow Changes In Conductancesupporting

confidence: 39%

The effects of tetraethylammonium and cobalt ions on responses to extrinsic current in toad rods.

Fain¹,

Quandt²

1980

The Journal of Physiology

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SUMMARY1. Double-barrel micropipettes were used to pass pulses of current in darkness into single rods in the isolated, perfused retina of the toad, Bufo marines.2. In normal Ringer solution, current pulses evoked non-linear changes in membrane potential which varied as a function of current amplitude and of time. Responses to currents of both polarities showed slow relaxations toward the base line during the pulse, and the steady-state I-V curve exhibited a prominent outward rectification.3. In Ringer containing 12 mM-TEA, the slow relaxation of voltage during outward current pulses was diminished, and the outward rectification was markedly reduced. In contrast Co2+, at a concentration in excess of that required to block Ca2+ spikes in rods, increased the receptor input resistance but did not reduce either the amplitude of the slow relaxation or the extent of outward rectification.4. These experiments indicated that the outward rectification of rods is predominantly due to a conductance which is gated by voltage rather than by entry of Ca2+. 5. Long-lasting after-potentials followed the termination of outward current pulses. In normal Ringer the after-potentials were hyperpolarizing and were accompanied by an increase in input conductance. In TEA, the afterpotentials were depolarizing and were also accompanied by an increase in input conductance. The after-depolarizations in TEA were enhanced by Sr2+ and blocked by Co2+. These experiments suggest that the hyperpolarizing and depolarizing afterpotentials are produced by different mechanisms, the hyperpolarizing by an increase in K+ conductance, and the depolarizing by an increase in Ca2+ conductance.

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Section: Afterpotentials and Slow Changes In Conductancesupporting

confidence: 39%

The effects of tetraethylammonium and cobalt ions on responses to extrinsic current in toad rods.

Fain¹,

Quandt²

1980

The Journal of Physiology

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“…There is conflicting evidence for retinal (Bulens et al, 1986) vs cortical (Regan & Maxner, 1987) dopaminergic system involvement in primates pattern vision. Nonetheless, activity of retinal dopaminergic neurons could also be modulated by extraretinal mechanisms (Stell, 1972). Thus, rather than a specific retinal or cortical involvement, an overall neurotransmitter/ neuromodulatory effect of dopamine along visual pathways may be suggested.…”

Section: Discussionsupporting

confidence: 39%

Selective effects of low doses of apomorphine on spatiotemporal contrast sensitivity in healthy volunteers: a double‐blind placebo‐ controlled study.

Blin¹,

Mestre²,

Masson³

et al. 1991

Brit J Clinical Pharma

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1. Apomorphine (1 and 5 micrograms kg‐1) and placebo were given to nine normal volunteers, using a Latin‐square design and double‐blind procedures. The visual perception of static and moving patterns (static and motion contrast sensitivity) was evaluated before and 15 min after the dose administration. 2. Apomorphine (1 and 5 micrograms kg‐1), as compared with placebo, led to a significant overall reduction of the visual perception of movement. This effect was dose‐related, and apomorphine (5 micrograms kg‐1) induced a more pronounced decrease in the visual perception of movement than apomorphine (1 microgram kg‐1). With apomorphine (5 micrograms kg‐1), the reduction was more pronounced for low spatial frequencies, and was linearly inversely correlated to the spatial frequency for a temporal frequency of 3 Hz. Finally, no significant effect of apomorphine was observed for sensitivity to static patterns. 3. Several non exclusive hypotheses may be suggested: The effects of apomorphine may result from stimulation of retinal D1‐ and/or D2‐dopaminergic receptors. Apomorphine may increase the surround inhibition of ganglion cells' receptive‐fields. This modification of the centre‐surround balance may explain the decrease in contrast sensitivity for low spatial frequencies. The specific effects of apomorphine on the visual perception of movement support the hypothesis that apomorphine preferentially affects the magnocellular pathway which mediates sensitivity to moving patterns.

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“…Furthermore, the retina is considerably simpler in structure than most of the rest of the central nervous system and has been extensively studied, both anatomically and physiologically (9). This is especially true for the outer plexiform layer, where photoreceptors synapse onto two kinds of secondorder cells, the horizontal cell and the bipolar cell (10).…”

mentioning

confidence: 49%

D-aspartate potentiates the effects of L-glutamate on horizontal cells in goldfish retina.

Ishida

Fain

1981

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

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The amino acids L-glutamate and L-aspartate depolarize HI horizontal cells in the perfused goldfish retina but only at millimolar concentrations. The effects of L-glutamate (but not of L-aspartate) are potentiated approximately 15-fold by exposure to D-aspartate. D-Aspartate blocks acidic amino acid uptake in goldfish retina, so that the potentiation ofL-glutamate may be produced by an increase in its effective concentration at the horizontal cell membrane. Because D-aspartate also augments the light responses of horizontal cells, our results are consistent with the possibility that L-glutamate is a neurotransmitter of cone photoreceptors in goldfish.Since the demonstration of the effects of amino acids on motoneurons nearly 20 years ago (1, 2), much attention has been given to the possibility that L-glutamate, L-aspartate, and other structurally similar acidic amino acids may function as synaptic transmitters in the vertebrate central nervous system. Exogenously applied L-glutamate has been shown to produce a depolarization or increase in spike firing in neurons from a variety of structures, including the cortex, hippocampus, cochlear nucleus, and thalamus (3). A Ca2+-dependent release of L-glutamate or L-aspartate has been demonstrated in several preparations, and there is evidence for a Na+-dependent, highaffinity uptake system for acidic amino acids in glia and some neurons (3)(4)(5).In spite of these findings, there is still considerable uncertainty whether L-glutamate or L-aspartate actually functions as a synaptic transmitter in vertebrates. Part of the reason for this is that these substances produce effects only at rather high concentrations and are usually nonspecific (6). Neurons depolarized by L-glutamate or by L-aspartate are usually also affected (and at similar concentrations) by D isomers of amino acids and by a large number of structurally similar analogues (2, 7). It seems possible that these compounds are not all reacting with the same membrane receptor (7,8) The retina offers several advantages for the study of synaptic transmitter mechanisms. Because it is possible in certain poikilotherms to remove the retina from its surrounding tissue and to maintain it in artificial media, it is possible to add amino acids and other drugs directly to the Ringer's solution. This reduces the uncertainty in estimates of drug concentration at the postsynaptic membrane. Furthermore, the retina is considerably simpler in structure than most of the rest of the central nervous system and has been extensively studied, both anatomically and physiologically (9). This is especially true for the outer plexiform layer, where photoreceptors synapse onto two kinds of secondorder cells, the horizontal cell and the bipolar cell (10).In this study we describe the effects of amino acids on one of the types of horizontal cells in the goldfish retina. This cell, called the H1 (or luminosity-type) cell, receives most of its synaptic input from the cone photoreceptors, predominantly those containing the red-sensitive p...

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The Morphological Organization of the Vertebrate Retina

Cited by 96 publications

References 246 publications

The effects of tetraethylammonium and cobalt ions on responses to extrinsic current in toad rods.

The effects of tetraethylammonium and cobalt ions on responses to extrinsic current in toad rods.

Selective effects of low doses of apomorphine on spatiotemporal contrast sensitivity in healthy volunteers: a double‐blind placebo‐ controlled study.

D-aspartate potentiates the effects of L-glutamate on horizontal cells in goldfish retina.

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