In retinal cones, membrane depolarization in darkness activates the cGMP-dependent conductance. A model of Ca homeostasis and the regulation of guanylate cyclase.

Miller, James L.; Korenbrot, Juan I.

doi:10.1085/jgp.101.6.933

Cited by 71 publications

(56 citation statements)

References 60 publications

(120 reference statements)

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“…2A). However in the physiological range between -45 and -70 mV, center responses remained largely unchanged (data not shown) (Miller and Korenbrot, 1993) but surround responses were significantly reduced (Fig. 3C).…”

Section: Discussionmentioning

confidence: 90%

Blue-Yellow Opponency in Primate S Cone Photoreceptors

Packer¹,

Verweij²,

Li³

et al. 2010

J. Neurosci.

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Section: Discussionmentioning

confidence: 90%

Blue-Yellow Opponency in Primate S Cone Photoreceptors

Packer¹,

Verweij²,

Li³

et al. 2010

J. Neurosci.

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“…These membrane patches are expected to contain only a single class of ion channels, those gated by cytoplasmic cGMP and regulated by light (Miller & Korenbrot, 1993a Na+ activity and the slope of the line that best fitted the data was 59-8 + 2'7 mV decade-' (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

“…The light-sensitive channels of vertebrate photoreceptors are among the more thoroughly characterized examples of cGMP-gated channels (for review see Yau & Baylor, 1989). In both rods (Baylor & Lamb, 1982) and cones (Miller & Korenbrot, 1993a), the channels are localized in the plasma membrane of the outer segment and this membrane contains no other ion channel. The channels are activated by the co-operative interaction of three to four cGMP molecules with a binding constant in the range of 6-30 uM in rods (Fesenko, Kolesnikov & Lyubarsky, 1985;Zimmerman & Baylor, 1986;Matthews & Watanabe, 1988;Ildefonse & Bennett, 1991;Quandt, Nicol & Schnetkamp, 1991) and 35-65 /SM in cones (Haynes & Yau, 1990;Picones & Korenbrot, 1992a;.…”

mentioning

confidence: 99%

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Spontaneous, ligand‐independent activity of the cGMP‐gated ion channels in cone photoreceptors of fish.

Picones

Korenbrot

1995

The Journal of Physiology

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1. We studied the electrical conductance of membrane patches detached from the outer segment of single cone photoreceptors isolated from striped bass retina. 2. Only a single class of ion channels exists in the plasma membrane of the cone outer segments; they are gated by cytoplasmic cGMP and select cations over anions, but distinguish poorly among cations. In the absence of added cGMP and of divalent cations, however, membrane patches detached from the outer segments exhibit a small conductance that ideally selects cations over anions, but distinguishes poorly between Na+ and Li+. 3. The cGMP-independent conductance does not arise from the effect of residual cGMP that may remain associated with the detached membrane, because treatment of the patch with cGMP-specific phosphodiesterase does not affect this conductance. 4. The cGMP-independent conductance is pharmacologically indistinguishable from that activated by cGMP Ca2+ and L-cis-diltiazem block both conductances at comparable concentrations and with similar quantitative characteristics. 5. We analysed the noise of Ca2+-or L-cis-diltiazem-dependent macroscopic currents both in the presence and in the absence of cGMP. In the presence of cGMP, the power density spectrum of the noise is well fitted by the sum of two Lorentzian components. The same function with similar corner frequencies fits the noise of the cGMP-independent currents. However, the total power in the current fluctuations is smaller in the absence of cGMP than in its presence; also, the ratio of the zero frequency asymptotes of the low over the high frequency components, Sj(0)/Sh(0), is larger in the absence of cGMP than in its presence. In contrast, the noise of the current through the leak conductance between electrode and membrane patch does not exhibit a Lorentzian component over the frequency tested. 6. The maximum value of the cGMP-dependent conductance over all membrane patches sampled varies over a range of about 10-fold. Over this range, however, there is a linear relationship between the cGMP-dependent and cGMP-independent conductances. The sum of our results suggest that the cGMP-independent conductance arises from the spontaneous activity of the ion channels ordinarily gated by cGMP. The cGMP-independent conductance is about 4 5 % of that measured under saturating cGMP concentrations. 7. In the absence of divalent cations and cGMP, the spontaneous channel activity sustains a mean (± S.D.) membrane conductance of 0-18 + 0-11 nS in the detached patches. This predicts an outer segment conductance in the intact cell that is about 500-fold larger in magnitude than the conductance actually measured in physiological solutions under bright light, when the cytoplasmic cGMP concentration is expected to be nil. This difference cannot be explained by the known effect of divalent cations on the unitary conductance of cGMP-gated channels alone. Divalent cations, therefore, must also control the probability of channel opening and, probably, prevent spontaneous channel activity.In a number of sensor...

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“…Accurate current kinetics in bass cones can only be measured under voltage clamp because the outer segment plasma membrane capacitance is large (58.1 ± 13.2 pF (Miller and Korenbrot, 1993b). Bass single cone photocurrents shown here were measured under voltage clamp in the whole-cell mode (Korenbrot, 2012a).…”

Section: Animal Models and Methods To Investigate Rod And Cone Transdmentioning

confidence: 99%

Speed, sensitivity, and stability of the light response in rod and cone photoreceptors: Facts and models

Korenbrot

2012

Progress in Retinal and Eye Research

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The light responses of rod and cone photoreceptors in the vertebrate retina are quantitatively different, yet extremely stable and reproducible because of the extraordinary regulation of the cascade of enzymatic reactions that link photon absorption and visual pigment excitation to the gating of cGMP-gated ion channels in the outer segment plasma membrane. While the molecular scheme of the phototransduction pathway is essentially the same in rods and cones, the enzymes and protein regulators that constitute the pathway are distinct. These enzymes and regulators can differ in the quantitative features of their functions or in concentration if their functions are similar or both can be true. The molecular identity and distinct function of the molecules of the transduction cascade in rods and cones are summarized. The functional significance of these molecular differences is examined with a mathematical model of the signal-transducing enzymatic cascade. Constrained by available electrophysiological, biochemical and biophysical data, the model simulates photocurrents that match well the electrical photoresponses measured in both rods and cones. Using simulation computed with the mathematical model, the time course of light-dependent changes in enzymatic activities and second messenger concentrations in non-mammalian rods and cones are compared side by side.

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In retinal cones, membrane depolarization in darkness activates the cGMP-dependent conductance. A model of Ca homeostasis and the regulation of guanylate cyclase.

Cited by 71 publications

References 60 publications

Blue-Yellow Opponency in Primate S Cone Photoreceptors

Blue-Yellow Opponency in Primate S Cone Photoreceptors

Spontaneous, ligand‐independent activity of the cGMP‐gated ion channels in cone photoreceptors of fish.

Speed, sensitivity, and stability of the light response in rod and cone photoreceptors: Facts and models

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