Two components of the receptor current are developed from distinct elementary signals in Limulus ventral nerve photoreceptor

1993 ◽  
Vol 22 (5) ◽  
pp. 341-350 ◽  
Author(s):  
K�roly Nagy ◽  
Klaus Contzen ◽  
Hennig Stieve
Keyword(s):  
Ventral Nerve Photoreceptor

Disturbing Gtp-Binding Protein Function Through Microinjection Into The Visual Cell Of Limulus

1992 ◽  
Vol 47 (11-12) ◽  
pp. 915-921 ◽  
Author(s):  
Henmg Stieve ◽  
Barbara Niemeyer ◽  
Klaus Aktories ◽  
Heidi E. Hamm
Keyword(s):  
Monoclonal Antibody ◽  
G Protein ◽  
Protein Function ◽  
Clostridium Botulinum ◽  
Functional Role ◽  
Electrical Response ◽  
Visual Cell ◽  
Gtp Binding ◽  
Dim Light ◽  
Ventral Nerve Photoreceptor

We have tested the action of three agents microinjected into the ventral nerve photoreceptor of Limulus on the electrical response to dim light. 1. A monoclonal antibody (mAb 4 A) against the Gɑ subunit of frog transducin reduces the size of the receptor current to 60%, suggesting an interaction with Gɑ in the Limulus photoreceptor. 2. Injection of Clostridium botulinum ADPribosyltransferase C 3 reduces the size to 46%; latency is not affected. The results imply that small GTP-binding proteins play a functional role in photoreception of invertebrates. 3. Injection of GD P-β-S reduces dose-dependently the size of the receptor current to 15% and prolongs the latency to 200%, presumably by reducing number and rate of G-protein activations

The influence of extracellular calcium ions on the light response of Limulus ventral nerve photoreceptor

1979 ◽  
Vol 19 (4) ◽  
pp. 351
Author(s):  
M. Bruns ◽  
M. Giesen ◽  
G. Maaz ◽  
M. Pflaum ◽  
H. Stieve
Keyword(s):  
Calcium Ions ◽  
Light Response ◽  
Extracellular Calcium ◽  
Ventral Nerve Photoreceptor

Extracellular Calcium, Magnesium, and Sodium Ion Competition in the Conductance Control of the Photosensory Membrane of Limulus Ventral Nerve Photoreceptor

1978 ◽  
Vol 33 (7-8) ◽  
pp. 574-579 ◽  
Author(s):  
H. Stieve ◽  
M. Bruns
Keyword(s):  
Membrane Potential ◽  
Calcium Concentration ◽  
Sodium Concentration ◽  
Extracellular Calcium ◽  
Magnesium Concentration ◽  
Sodium Ions ◽  
Extracellular Calcium Concentration ◽  
Calcium Magnesium ◽  
Extracellular Sodium ◽  
Ventral Nerve Photoreceptor

Abstract The membrane potential in the dark and the saturated response height of the ventral nerve photoreceptor of Limulus was measured by an intracellular electrode while the external concentration of calcium, magnesium and sodium ions was varied. Decreasing the extracellular calcium concentration from 10-2 mol/l causes a calcium-dependent lowering of the dark membrane potential and at very low concentrations (<10-8 mol/l a reversal to ca. +5 to +11 mV, if the external magnesium concentration is also low. Also, the light response diminishes with decreasing extracellular calcium concentration and disappears at a concentration of 10-9 mol/l. External magnesium can substitute for certain properties of extracellular calcium. Lowering the extracellular sodium concentration from 543 mmol/l to 30 - 50 mmol/1 reduces the dark membrane potential and the light responses at normal calcium concentration, whereas at low calcium concentration it causes a substantial rise of both. Interpretation: The results are in accordance with our working hypothesis that a strong reduction of the external calcium (and magnesium) concentration causes a calcium concentration dependent opening of “ light channels” in the dark. Additional lowering the extracellular sodium concentration counteracts this effect; opening and closing of light channels is controlled by negative binding sites on the cell membrane for which calcium and sodium ions compete with an antagonistic action.

scholarly journals Light-Evoked and Spontaneous Discrete Waves in the Ventral Nerve Photoreceptor of Limulus

1973 ◽  
Vol 61 (5) ◽  
pp. 552-571 ◽  
Author(s):  
Stephen Yeandle ◽  
Joel B. Spiegler
Keyword(s):  
Light Pulse ◽  
Visual Pigment ◽  
Time Dependent ◽  
Photon Absorption ◽  
Short Pulses ◽  
Short Light Pulse ◽  
Pigment Molecule ◽  
The Waves ◽  
Ventral Nerve Photoreceptor

Discrete waves, recorded from the ventral nerve photoreceptor, occur in the light and in the dark. Spontaneous waves, on the average, are smaller than light-evoked waves. This suggests that not all spontaneous waves can arise from spontaneous changes in the visual pigment molecule identical to changes induced by photon absorption. Spontaneous and light-evoked waves are statistically independent of each other. This is shown by determination of frequency of response as a function of pulse energy for short pulses and determination of the distribution of intervals between waves evoked by steady lights. The available data can be explained by two models. In the first each photon produces a time-dependent excitation that goes to zero the instant the wave occurs so that the number of effective absorptions from a short light pulse equals the number of waves produced by the light pulse. In the second the excitation produced by photon absorption is unaffected by the occurrence of the waves so that the number of waves produced from a short light pulse may be different from the number of effective absorptions. Present results do not allow a choice between the two models.

Single Photon-Evoked Events Of The Ventral Nerve Photoreceptor Cell Of Limulus Facilitation, Adaptation And Dependence Of Lowered External Calcium

1991 ◽  
Vol 46 (5-6) ◽  
pp. 461-486 ◽  
Author(s):  
H. Stieve ◽  
H. Reuß ◽  
H. T. Hennig ◽  
J. Klomfaß
Keyword(s):  
Calcium Concentration ◽  
Calcium Release ◽  
Light Adaptation ◽  
Single Photon ◽  
Calcium Deficiency ◽  
Magnesium Concentration ◽  
Calcium Stores ◽  
Calcium Dependent ◽  
Ventral Nerve Photoreceptor ◽  
External Calcium

Bumps, the elementary excitatory events of the Limulus ventral nerve photo receptor following a weak flash of light were recorded under voltage clamp conditions. The statistical distribution of various bump parameters and their changes caused by weak conditioning pre-illumination are described, and the influence of lowered external Ca2+-concentration together with normal or raised Mg2+-concentration (15 °C).1) Weak conditioning pre-illumination causes desensitization: the bump current amplitude, bump duration , bump area (current-integral), and the bump latency are diminished, the more, the stronger the conditioning flash, i.e. the light adaptation. Very weak conditioning pre-illumination causes facilitation, expressed by an increase in number and size of the observed bumps. The average bump latency, however, is already shortened under these conditions.2) Lowering the external Ca2+-concentration from 10 mmol/l to 250 (µmol/1 has its primary effect on the dark -adapted photoreceptor (without substantially reducing the ability for light adaptation ). It causes the following average changes: the amplitudes, durations, current-integrals, and the latencies of current bumps are greatly enlarged and the number of bumps is raised.3) Raised magnesium concentration from 50 to 100 mmol/l can partially compensate for the lack of calcium ; however, it enhances the effect of calcium deficiency on the latency, i.e. it further enlarges the average latencies. The results can be explained on the basis of our model of bump generation by two assumptions.1) Lowering the external calcium concentration causes a decrease in the cytosolic Ca2+-level without substantially reducing the intracellular calcium stores from which the light-adapting calcium release is fed. The lowered cytosolic Ca2+-concentration induces an “extra” dark adaptation resulting in greater bumps and more bumps exceeding the threshold of recognition. The bump latency, however, which behaves differently from all other bump parameters, is determined by a separate calcium -dependent reaction where magnesium competes with calcium antagonistically. 2) Facilitation is due to cooperativity of transmitter binding in order to open the ion channels

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