Bumps, the Elementary Excitatory Responses of Invertebrates

Stieve, H.

doi:10.1007/978-3-642-70444-4_13

Cited by 32 publications

(43 citation statements)

References 84 publications

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“…D ata from four photoreceptors which were sta ble enough to perform all three phases of the ex periment consecutively, is summarized in Figure IB . Our results confirm those from earlier studies (reviewed in Stieve, 1986) and are described only briefly. In physiological saline, the conditioning flash led to light adaptation and the average bump amplitude and current integral were smaller by 48% and 59% , respectively.…”

Section: Bumps In Dark and Light Adaptation In Normal And Reduced Casupporting

confidence: 92%

“…Bath ing the photoreceptors in low calcium saline did not significantly impair bump adaptation. Earlier studies showed that variation of the external calcium concentration between less than 1 jiM and 40 m M only moderately influenced bump adapta tion (Stieve andBruns, 1980, 1983). This indicates that the steady state Ca; before the conditioning stimulus is of relatively little importance for the process of light adaptation.…”

Section: Effect O F Calcium On Response Generation and Adaptationmentioning

confidence: 96%

“…In the ventral photoreceptor of the horseshoe crab Lim ulus polyphemus the absorption of a single photon leads to a small transient receptor current or depo larization called "quantal bump" (Yeandle, 1958). Bright illumination evokes a macroscopic photore sponse that consists of many temporarily and spa tially fused bumps (Dogde, Knight and Toyoda, 1968;Brown and Coles, 1979;Stieve, 1986 The electrical photoresponse is accompanied by a rise in the concentration of free calcium ions in the cytoplasm (Brown, Brown and Pinto, 1977;Maaz and Stieve, 1980;Levy and Fein, 1985). In the ventral photoreceptor the endoplasmic reticu lum forms an extensive network in which calcium is stored and from which it is released after illumi nation (Payne, Walz, Levy and Fein, 1988;Feng, Carson, Morgan, Walz and Fein, 1994).…”

Section: Introductionmentioning

confidence: 99%

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Effects of Calcium and Cyclopiazonic Acid on the Photoresponse in the Limulus Ventral Photoreceptor

Dorlöchter

Yuan

Stieve

1999

Zeitschrift Für Naturforschung C

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Phototransduction, Current Components, Light Adaptation, Bumps, CPA 1. Single-photon responses (bumps) and small macroscopic photocurrents were studied in ventral photoreceptors of the horseshoe crab Limulus. Lowering the calcium concentration in the bath from 10 mM to 250 fiM led to increased bump size. Adaptation of the cells by a moderately bright conditioning flash was not impaired.2. Pressure-injection of 1.2 mM EG TA into the dark-adapted cells resulted in reduced bump size. EG TA weakened the effect of the conditioning light flash although it did not completely abolish light adaptation.3. The microsomal calcium-ATPase inhibitor cyclopiazonic acid strongly desensitized the cells, and bumps were suppressed below detection. When the bathing saline contained 10 m M calcium, macroscopic photoresponses after extracellular application of the agent had ampli tudes smaller than under control conditions but normal response kinetics: The response to a light step still consisted of a fast transient photocurrent and a much smaller plateau. How ever, when applied in calcium-free bathing saline, cyclopiazonic acid additionally influenced the waveform of the photoresponse. The clear distinction between transient and plateau was no longer possible, and the photocurrent appeared "square".4. Our results support the idea that a transient elevation of the cytosolic calcium concentra tion is obligatory for light adaptation in the ventral photoreceptor. It is also obligatory for the generation of the so-called C2 component of the photocurrent which is represented by "standard" bumps and the fast transient phase of a prolonged response. However, a rise in cytosolic calcium appears not necessary for the initiation of a slow electrical photoresponse.

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Section: Bumps In Dark and Light Adaptation In Normal And Reduced Casupporting

confidence: 92%

Section: Effect O F Calcium On Response Generation and Adaptationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Effects of Calcium and Cyclopiazonic Acid on the Photoresponse in the Limulus Ventral Photoreceptor

Dorlöchter

Yuan

Stieve

1999

Zeitschrift Für Naturforschung C

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“…It has been suggested that the latency and amplification in the transduction process are two separate processes (Stieve & Bruns, 1983;Stieve, 1986;Kraemer, Lederhofer & Schnakenberg, 1989;Schnakenberg, 1989;Stieve, ReuB, Hennig & KlomfaB, 1991). This assumption is supported by the data presented in Figs 2A and 3B.…”

Section: Discussionsupporting

confidence: 81%

“…The relationship between stimulus intensity and response size has been studied by a number of authors (for reviews see Stieve, 1986;Nagy, 1991). The log-log representation of the current maximum and the stimulus intensity suggests a power law of I.a.…”

Section: Discussionmentioning

confidence: 99%

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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The Response of the Limulus Photoreceptor Cell to the Absorption of Single Photons

Stieve

1988

Ber Bunsenges Phys Chem

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The response of the visual cell of the horseshoe crab Limulus to light stimuli is described. Due to the absorption of a single photon, a rhodopsin molecule is light‐activated and starts a sequence of causal steps which lead to the generation of a relatively large elementary excitatory response, the “bump”. A bump is based on the concerted transient opening of a large number of sodium ion‐preferring channels through the cell membrane. The bump generating mechanism is discussed. – The “macroscopic” light response to higher stimulus intensities is believed to consist of a fused volley of bumps. Its intensity dependence is discussed. A conditioning pre‐illumination usually desensitizes the visual cell transiently. However, very weak pre‐illumination may cause an increase in sensitivity, “facilitation”.

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Bumps, the Elementary Excitatory Responses of Invertebrates

Cited by 32 publications

References 84 publications

Effects of Calcium and Cyclopiazonic Acid on the Photoresponse in the Limulus Ventral Photoreceptor

Effects of Calcium and Cyclopiazonic Acid on the Photoresponse in the Limulus Ventral Photoreceptor

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

The Response of the Limulus Photoreceptor Cell to the Absorption of Single Photons

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