Cobalt ions inhibit negative feedback in the outer retina by 
blocking hemichannels on horizontal cells

Fahrenfort, Iris; Sjoerdsma, Trijntje; Ripps, Harris; Kamermans, Maarten

doi:10.1017/s095252380421402x

Cited by 34 publications

(34 citation statements)

References 31 publications

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“…It has been shown that a low dose of Co 2ϩ can inhibit feedback without affecting the Ca 2ϩ current of the cones directly (Fahrenfort et al, 2004). If feedback from HCs to cones is the underlying mechanism of the increase of the response to sinusoidal stimulation, then blocking feedback should abolish this increase.…”

Section: Gain Control In the Outer Retinamentioning

confidence: 99%

Lateral Gain Control in the Outer Retina Leads to Potentiation of Center Responses of Retinal Neurons

VanLeeuwen¹,

Fahrenfort²,

Sjoerdsma³

et al. 2009

J. Neurosci.

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The retina can function under a variety of adaptation conditions and stimulus paradigms. To adapt to these various conditions, modifications in the phototransduction cascade and at the synaptic and network levels occur. In this paper, we focus on the properties and function of a gain control mechanism in the cone synapse. We show that horizontal cells, in addition to inhibiting cones via a "lateral inhibitory pathway," also modulate the synaptic gain of the photoreceptor via a "lateral gain control mechanism." The combination of lateral inhibition and lateral gain control generates a highly efficient transformation. Horizontal cells estimate the mean activity of cones. This mean activity is subtracted from the actual activity of the center cone and amplified by the lateral gain modulation system, ensuring that the deviation of the activity of a cone from the mean activity of the surrounding cones is transmitted to the inner retina with high fidelity.

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Section: Gain Control In the Outer Retinamentioning

confidence: 99%

Lateral Gain Control in the Outer Retina Leads to Potentiation of Center Responses of Retinal Neurons

VanLeeuwen¹,

Fahrenfort²,

Sjoerdsma³

et al. 2009

J. Neurosci.

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“…Existing research has shown that sub-millimolar concentrations of cobalt (50-100·M) block the horizontal cell feedback of cones in turtles (Thoreson and Burkhardt, 1990;Vigh and Witkovsky, 1999) and in fish (Fahrenfort et al, 2004). Injections of either cobalt chloride (Sigma-Aldrich) or saline were made at the limbus of the left eye using a 30-gauge needle.…”

Section: Intraocular Injectionsmentioning

confidence: 99%

“…Yuan and Yang (Yuan and Yang, 1997) suggest that cobalt-induced signal suppression results from a blockage of glutamate uptake by photoreceptors. Cobalt is known to block horizontal cell-mediated feedback on cones in goldfish retina (Fahrenfort et al, 2004;Thoreson and Burkhardt, 1990). The result of blocking negative feedback of horizontal cells on cones is that the cone synapse is rendered out of its working range (Kamermans et al, 1998;Kamermans et al, 2001).…”

Section: Origin Of Intermediary Peaks: Cobalt Treatment and Intermedimentioning

confidence: 99%

Retinal processing and opponent mechanisms mediating ultraviolet polarization sensitivity in rainbow trout (Oncorhynchus mykiss)

Ramsden

Anderson

Mussi

et al. 2008

Journal of Experimental Biology

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SUMMARYA number of teleost fishes have photoreceptor mechanisms to detect linearly polarized light. We studied the neuronal mechanism underlying this ability. It was found that a polarized signal could be detected in rainbow trout (Oncorhynchus mykiss) both in the electroretinogram (ERG) and in the compound action potential (CAP) measured in the optic nerve, indicating a strong retinal contribution to the processing of polarized light. The CAP recordings showed a W-shaped sensitivity curve, with a peak at 0°, 90°a nd 180°, consistent with processes for both vertical and horizontal orientation. By contrast, the ERG recordings reveal a more complex pattern. In addition to the peaks at 0°, 90° and 180°, two additional peaks appeared at 45° and 135°. This result suggests a specialized contribution of the outer retina in the processing of polarized light. The spectral sensitivity of the mechanisms responsible for these intermediate peaks was studied using chromatic adaptation. Here we show that long wavelength-sensitive (LWS) cone mechanism adaptation shifted the intermediate peaks towards 90°, whereas ultraviolet-sensitive (UVS) cone mechanism adaptation shifted the peaks away from 90° towards either 0° or 180°. These results provide further confirmation that the 90° peak is dominated by the LWS cone mechanism and the 0° and 180° peaks are dominated by the UVS cone mechanism. In addition, a pharmacological approach was used to examine the retinal neural mechanisms underlying polarization sensitivity. The effect of blocking negative feedback from horizontal cells to cones on the ERG was studied by making intraocular injections of low doses of cobalt, known to block this feedback pathway. It was found that the intermediate peaks seen in the ERG polarization sensitivity curves were eliminated after application of cobalt, suggesting that these peaks are due to outer retinal inhibition derived from feedback of horizontal cells onto cones. A simple computational model was developed to evaluate these results. The model consists of opponent and non-opponent processing elements for the two polarization detectors. This model provides a first approximation analysis suggesting that opponent processing occurs in the outer retina for polarization vision. Although it seems that polarization vision uses a slightly more complicated coding scheme than colour vision, the results presented in this paper suggest that opponent and non-opponent channels process polarization information.

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“…Amiloride is known to inhibit some ENaCs (Garty and Palmer, 1997), acid sensing ion channels (Waldmann et al, 1997), transient receptor potential channels (Inoue et al, 2001;Vulcu et al, 2004), and glutamate-gated channels (Manev et al, 1990). Divalent cations have been shown to block inhibitory feedback from HCs, and no conclusive explanation for this has been put forth (Thoreson and Burkhardt, 1990;Vigh and Witkovsky, 1999;Fahrenfort et al, 2004). Divalent cations block ENaC currents (Sheng et al, 2002).…”

Section: Horizontal Cells Could Modulate Cleft Ph Via An Amiloridesenmentioning

confidence: 99%

Proton-Mediated Feedback Inhibition of Presynaptic Calcium Channels at the Cone Photoreceptor Synapse

Vessey

Stratis²,

Daniels³

et al. 2005

J. Neurosci.

115

136

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Generation of center-surround antagonistic receptive fields in the outer retina occurs via inhibitory feedback modulation of presynaptic voltage-gated calcium channels in cone photoreceptor synaptic terminals. Both conventional and unconventional neurotransmitters, as well as an ephaptic effect, have been proposed, but the intercellular messaging that mediates the inhibitory feedback signal from postsynaptic horizontal cells (HCs) to cones remains unknown. We examined the possibility that proton concentration in the synaptic cleft is regulated by HCs and that it carries the feedback signal to cones. In isolated, dark-adapted goldfish retina, we assessed feedback in the responses of HCs to light and found that strengthened pH buffering reduced both rollback and the depolarization to red light. In zebrafish retinal slices loaded with Fluo-4, depolarization with elevated K ϩ increased Ca signals in the synaptic terminals of cone photoreceptors. Kainic acid, which depolarizes HCs but has no direct effect on cones, depressed the K ϩ -induced Ca signal, whereas CNQX, which hyperpolarizes HCs, increased the Ca signals, suggesting that polarization of HCs alters inhibitory feedback to cones. We found that these feedback signals were blocked by elevated extracellular pH buffering, as well as amiloride and divalent cations. Voltage clamp of isolated HCs revealed an amiloride-sensitive conductance that could mediate modulation of cleft pH dependent on the membrane potential of these postsynaptic cells.

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Cobalt ions inhibit negative feedback in the outer retina by blocking hemichannels on horizontal cells

Cited by 34 publications

References 31 publications

Lateral Gain Control in the Outer Retina Leads to Potentiation of Center Responses of Retinal Neurons

Lateral Gain Control in the Outer Retina Leads to Potentiation of Center Responses of Retinal Neurons

Retinal processing and opponent mechanisms mediating ultraviolet polarization sensitivity in rainbow trout (Oncorhynchus mykiss)

Proton-Mediated Feedback Inhibition of Presynaptic Calcium Channels at the Cone Photoreceptor Synapse

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