Calcium ion, an intracellular messenger of light adaptation, also participates in excitation of Limulus photoreceptors.

Bolsover, Stephen R.; Brown, J. E.

doi:10.1113/jphysiol.1985.sp015751

Cited by 85 publications

(84 citation statements)

References 19 publications

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“…One of the components may be activated by intracellular calcium ions while the other two are activated by different transmitters. This hypothesis is also discussed by Bolsover & Brown (1985), Payne et al (1986b) and Nagy (1990Nagy ( , 1991.…”

Section: Discussionmentioning

confidence: 91%

“…The space clamp is highly accurate before stimulation. Brown, Harary & Waggoner (1979) showed that spatial non-uniformity of the intracellular voltage with a twoelectrode voltage clamp is smaller than 2 mV in Limulus ventral nerve photoreceptors (see also Bolsover & Brown, 1985). If there were a unique reversal voltage for the light-activated conductance, then at that voltage the opening of channels would cause no current anywhere and the space clamp would be preserved.…”

Section: Discussionmentioning

confidence: 99%

“…We assume that the change in the extracellular calcium concentration changed the portion of the components contributing to the total current measured by Bolsover & Brown (1985). Therefore, the slope in the log-log plot of the current vs. light intensity also changed (see their Fig.…”

Section: Discussionmentioning

confidence: 99%

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Three components in the light‐induced current of the Limulus ventral photoreceptor.

Deckert

Nagy

Helrich

et al. 1992

The Journal of Physiology

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SUMMARY1. Light-induced currents were measured in Limulus ventral nerve photoreceptors using a two-electrode voltage clamp. Three kinetically distinct components in the light-induced current could be distinguished by varying the light adaptation state of the photoreceptor and the intensity of the stimulus light.2. The components could be partly separated by choosing appropriate stimulus intensities and dark adaptation time. Thus the properties of the components could be separately studied. The first component is the first to recover after a light adaptation, appears temporally first in the light-induced response, has the lowest activation threshold and is the smallest. The second component needs a longer time to recover after an adapting illumination and its kinetics differ from that of the other components. Applying a bright stimulus to a dark-adapted cell a third component can be observed late in the response.3. The time to peak of the first and the third components depended on the stimulus intensity, but not on the dark adaptation time. The time to peak of the second component became shorter the longer the dark adaptation time. For a constant adaptation state the time to the maximum of component 2 was independent, but those of components 1 and 3 were dependent on the membrane voltage.4. To exclude the possibility of the contribution of voltage-gated currents, lightactivated currents were measured at clamp potentials more negative than -50 mV after adding 4-aminopyridine into the bath solution or injecting tetraethylammonium chloride into the cell. The properties of the three components remained unchanged under these conditions. 5. The I-V curve of the first component was flat at negative membrane potentials and had a strong outward rectification at positive membrane potentials. The I-V curve of component 3 showed a negative resistance at potentials more negative than about -30 mV. In contrast, the I-V curve for the second component was always nearly linear.6. No membrane potential was found where the light-induced current was zero.Instead, current traces close to the reversal potential showed a complex waveform indicating different reversal potentials for the three components.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Three components in the light‐induced current of the Limulus ventral photoreceptor.

Deckert

Nagy

Helrich

et al. 1992

The Journal of Physiology

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“…These studies may have failed to make optimal use of aequorin. When used optimally, aequorin can detect resting levels of Cai within dark-adapted ventral photoreceptors (Bolsover and Brown, 1985;O'Day and GrayKeller, 1989). However, the low resting aequorin luminescence under these conditions, the nonlinear relationship between Cai and luminescence, and the localized nature of the InsP~-induced increase of Cai would make it difficult to quantify any elevation of Cai remaining after an injection of InsP3, even if lingering aequorin luminescence were detectable by an improved method.…”

Section: Introductionmentioning

confidence: 99%

A lingering elevation of Cai accompanies inhibition of inositol 1,4,5 trisphosphate-induced Ca release in Limulus ventral photoreceptors.

Levy

Payne

1993

The Journal of General Physiology

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Injection of inositol 1,4,5 trisphosphate (ImPs) into Limulus ventral photoreceptors causes an elevation of intracellular free Ca concentration (Cai) and depolarizes the photoreceptors. When measured with the photoprotein aequorin, the InsPs-induced Cai increase follows the time course of depolarization and declines within 1-2 s. However, sensitivity to further injections of InsP3 remains suppressed for several tens of seconds. The possibility that the suppression of Ca release (feedback inhibition) is due to a small lingering elevation of Cai, below the existing detection limit of aequorin, was investigated by measuring Cai with Ca-sensitive electrodes. Double-barreled, Ca-selective microelectrodes were used to pressure inject InsPs and measure Cai at the same point. Light or InsPs injections into the light-sensitive compartment depolarized the photoreceptors and induced an elevation of Cai that persisted for tens of seconds. Injections of InsP3 during the decay of Cai showed that sensitivity to InsP3 recovered as resting Cai approached the prestimulus level. The relationship between elevated Cai and feedback inhibition was very steep. An elevation of Cai of 1 o.M or more was associated with inhibitions of 79 +-12.4% (SEM; n = 7) for the InsP~-induced Cai increase and of 76 ± 8% for depolarizations. With a residual Cai elevation of 0.01 o.M or less, the mean inhibition was 10 ± 7.4% for InsPs-induced Cai increase and 6.6 ± 4% for InsPz-induced depolarization. Injections of InsP3 into a light-insensitive compartment within the cell induced elevations of Cai with no associated depolarizations or feedback inhibition. To verify that a sustained elevation of Ca i is necessary for inhibition of InsPz-induced Cai increase and depolarization, we injected ethyleneglycol-bis-(13-aminoethylether)-N,N'-tetraacetic acid (EGTA) between two injections of InsP3. Injection of 1 mM EGTA or the related Ca chelator BAPTA, delivered 750 ms after the first injection of InsPs, restored the peak depolarization caused by the second injection of InsP3 to > 80 ± 3% of control, compared with 13 ± 8% without an intervening injection of EGTA. Measurement of Cai with aequorin showed that an intervening injection of EGTA partially restored the InsP3-induced Ca i increase.

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“…In particular, the photoresponse in Drosophila was found to be absolutely dependent on PLC activity. Until recently, it was thought that IP 3 is the second messenger involved in the photoresponse in invertebrates because a brief injection of IP 3 mimicked the quantal response to light (4,5) and IP 3 -induced Ca 2ϩ release resulted in membrane depolarization in the Limulus ventral photoreceptor (14) by activating Ca 2ϩ /Na ϩ exchange (15,16). More recent evidence, however, indicates that the mechanism is more complex.…”

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confidence: 99%

Evidence for the Involvement of Inositol Trisphosphate but Not Cyclic Nucleotides in Visual Transduction in HermissendaEye

Sakakibara¹,

Inoue²,

Yoshioka³

1998

Journal of Biological Chemistry

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Although several second messengers are known to be involved in invertebrate photoresponses, the mechanism underlying invertebrate phototransduction remains unclear. In the present study, brief injection of inositol trisphosphate into Hermissenda photoreceptors induced a transient Na ؉ current followed by burst activity, which accurately reproduced the native photoresponse. Injection of Ca 2؉ did not induce a significant change in the membrane potential but potentiated the native photoresponse. Injection of a Ca 2؉ chelator decreased the response amplitude and increased the response latency. Injection of cGMP induced a Ca 2؉ -dependent, transient depolarization with a short latency. cAMP injection evoked Na ؉ -dependent action potentials without a rise in membrane potential. Taken together, these results suggest that phototransduction in Hermissenda is mediated by Na ؉ channels that are directly activated by inositol trisphosphate without mobilization of cytosolic Ca 2؉ .

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Calcium ion, an intracellular messenger of light adaptation, also participates in excitation of Limulus photoreceptors.

Cited by 85 publications

References 19 publications

Three components in the light‐induced current of the Limulus ventral photoreceptor.

Three components in the light‐induced current of the Limulus ventral photoreceptor.

A lingering elevation of Cai accompanies inhibition of inositol 1,4,5 trisphosphate-induced Ca release in Limulus ventral photoreceptors.

Evidence for the Involvement of Inositol Trisphosphate but Not Cyclic Nucleotides in Visual Transduction in HermissendaEye

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