scholarly journals Electrophysiological properties of isolated photoreceptors from the eye of Lima scabra.

1991 ◽  
Vol 97 (1) ◽  
pp. 17-34 ◽  
Author(s):  
E Nasi
Keyword(s):  
Light Adaptation ◽  
Sea Water ◽  
Bright Light ◽  
Receptor Potential ◽  
Input Resistance ◽  
Photoreceptor Cells ◽  
Continuous Illumination ◽  
Moderate Intensity ◽  
Electrophysiological Properties ◽  
Voltage Dependent

Photoreceptor cells were enzymatically dissociated from the eye of the file clam, Lima scabra. Micrographs of solitary cells reveal a villous rhabdomeric lobe, a smooth soma, and a heavily pigmented intermediate region. Membrane voltage recordings using patch electrodes show resting potentials around -60 mV. Input resistance ranges from 300 M omega to greater than 1 G omega, while membrane capacitance is of the order of 50-70 pF. In darkness, quantum bumps occur spontaneously and their frequency can be increased by dim continuous illumination in a fashion graded with light intensity. Stimulation with flashes of light produces a depolarizing photoresponse which is usually followed by a transient hyperpolarization if the stimulus is sufficiently intense. Changing the membrane potential with current-clamp causes the early phase to invert around +10 mV, while the hyperpolarizing dip disappears around -80 mV. With bright light, the biphasic response is followed by an additional depolarizing wave, often accompanied by a burst of action potentials. Both Na and Ca ions are required in the extracellular solution for normal photoexcitation: the response to flashes of moderate intensity is greatly degraded either when Na is replaced with Tris, or when Ca is substituted with Mg. By contrast, quantum bumps elicited by dim, sustained light are not affected by Ca removal, but they are markedly suppressed in a reversible way in 0 Na sea water. It was concluded that the generation of the receptor potential is primarily dependent on Na ions, whereas Ca is probably involved in a voltage-dependent process that shapes the photoresponse. Light adaptation by repetitive flashes leads to a decrease of the depolarizing phase and a concomitant enhancement of the hyperpolarizing dip, eventually resulting in a purely hyperpolarizing photoresponse. Dark adaptation restores the original biphasic shape of the photoresponse.

scholarly journals Voltage-dependent K+ Channels Improve the Energy Efficiency of Signalling in Blowfly Photoreceptors

2016 ◽  
Author(s):  
Francisco J. H. Heras ◽  
John Anderson ◽  
Simon B. Laughlin ◽  
Jeremy E. Niven
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Negative Feedback ◽  
Light Adaptation ◽  
Bright Light ◽  
Spiking Neurons ◽  
Delayed Rectifier ◽  
Voltage Response ◽  
Functional Requirements ◽  
Voltage Dependent

AbstractVoltage-dependent conductances in many spiking neurons are tuned to reduce action potential energy consumption, so improving the energy efficiency of spike coding. However, the contribution of voltage-dependent conductances to the energy efficiency of analogue coding, by graded potentials in dendrites and non-spiking neurons, remains unclear. We investigate the contribution of voltage-dependent conductances to the energy efficiency of analogue coding by modelling blowfly R1-6 photoreceptor membrane. Two voltage-dependent delayed rectifier K+ conductances (DRs) shape the membrane's voltage response and contribute to light adaptation. They make two types of energy saving. By reducing membrane resistance upon depolarisation they convert the cheap, low bandwidth membrane needed in dim light to the expensive high bandwidth membrane needed in bright light. This investment of energy in bandwidth according to functional requirements can halve daily energy consumption. Second, DRs produce negative feedback that reduces membrane impedance and increases bandwidth. This negative feedback allows an active membrane with DRs to consume at least 30% less energy than a passive membrane with the same capacitance and bandwidth. Voltage gated conductances in other non-spiking neurons, and in dendrites, might be organized to make similar savings.

Ionic mechanisms of phototransduction in photoreceptor cells from the epistellar body of the octopus eledone cirrhosa

1999 ◽  
Vol 202 (8) ◽  
pp. 977-986
Author(s):  
C.S. Cobb ◽  
R. Williamson
Keyword(s):  
Time Course ◽  
Sea Water ◽  
Light Flash ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Evoked Response ◽  
Na Channel ◽  
External Application ◽  
Ionic Mechanisms ◽  
Potential Activity

Intracellular recordings were made from extraocular photoreceptor cells within isolated epistellar bodies of the lesser or northern octopus Eledone cirrhosa. The cells had resting potentials around −41+/−5 mV (mean +/− s.d., N=60) and showed light-flash-induced membrane depolarisation. The evoked response to a brief light flash consisted of a transient peak depolarisation, followed by a plateau component. The magnitude of the light-induced peak depolarisation response was decreased by bathing the epistellar body in artificial sea water (ASW) low in Na+, where choline+ replaced Na+, or by passing steady depolarising current. Replacement of external Na+ by Li+ had no effect on the light-stimulated response. The external application of the Na+ channel blocker tetrodotoxin (3 micromol l-1) increased the light-evoked response, but this was accompanied by a loss of action potential activity. The amplitude and duration of the response to a light flash was increased by bathing the epistellar body in ASW low in Ca2+, or in ASW containing 10 mmol l-1 Co2+, and after intracellular microinjection of the Ca2+ buffer EGTA. Intracellular microinjection of Ca2+ or inositol 1,4,5-trisphosphate, or external application of the phospholipase C inhibitor U-73122, had no apparent effect on the light-evoked response. These results are consistent with the interpretation that (1) the majority of the light-induced inward current is carried by Na+, probably via a non-selective cation channel, and (2) an increase in the intracellular free Ca2+ concentration, mediated by the phototransduction process, is involved in regulating the light-induced inward photocurrent and thus, in effect, determines the amplitude, time course and sensitivity of the receptor potential.

Über die Ionen-Abhängigkeit des Rezeptorpotentials der Retina von Astacus leptodactylus / The Ion-dependence of the Receptor Potential of the Visual Cell of the Crayfish

1971 ◽  
Vol 26 (5) ◽  
pp. 457-470 ◽  
Author(s):  
H. Stieve ◽  
Chr. Wirth
Keyword(s):  
Light Adaptation ◽  
Ionic Composition ◽  
Latency Period ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Constant Stimulus ◽  
Visual Cell ◽  
Ion Pump ◽  
Sodium Ions ◽  
Astacus Leptodactylus

The mass response of the photoreceptor cells of the isolated crayfish-retina (Astacus leptodactylus) (receptor potential ReP) resulting from short and long light stimuli, has been measured with external electrodes.The ionic composition of the saline by which the preparation was perfused was changed and the influence of those changes on the ReP was measured under constant stimulus conditions.When all sodium ions are substituted by potassium ions, the height of the ReP is reversibly both decreased and shortened (Figs. 3 and 4).When all sodium ions are almost substituted by choline ions, (the remaining sodium concentration at the photoreceptor cells being less than 1 mMol/Z) the sensitivity to light adaptation is drastically and reversibly increased. Mainly due to light adaptation the ReP becomes smaller and shorter whereas the latency period increases (Figs. 5 - 8).If the concentration of extracellular calcium is reduced to less than 0.1 mMol/l, the decrease of the REP is considerably and reversibly slowed down while the increase of the REP remains almost unchanged (Fig. 9). If magnesium ions are also lacking the effect is even more pronounced (Figs. 10 and 11).All these changes of the ReP are probably due to actions of the ions on the membrane of the photoreceptor cells or its immediate vicinity.The results do not allow an unequivocal decision whether the ReP is due to an increased conductance (CIM) of the photoreceptor cell membrane or due to a change in the action of an electrogenic ion pump (EPM). But considering the results as a whole, and especially those from the low Ca- and low Mg-experiments, it seems unlikely that the ReP is caused by an EPM.

Light-induced retinal degeneration in rdgB (retinal degeneration B) mutant of Drosophila: Electrophysiological and morphological manifestations of degeneration

1989 ◽  
Vol 2 (6) ◽  
pp. 529-539 ◽  
Author(s):  
Chaim T. Rubinstein ◽  
Shoshana Bar-Nachum ◽  
Zvi Selinger ◽  
Baruch Minke
Keyword(s):  
Retinal Degeneration ◽  
Early Stage ◽  
Light And Electron Microscopy ◽  
Bright Light ◽  
Light Response ◽  
Photoreceptor Cells ◽  
Dark Cycle ◽  
Voltage Dependent ◽  
Normal Light ◽  
Two Phases

AbstractQuantitative light and electron microscopy was used to monitor the extent of retinal degeneration as a function of age and temperature in the white-eyed rdgBKS222 mutant of Drosophila melanogaster. Parallel measurements of the electroretinogram (ERG) of the degenerating retina reveal a new phenomenon – the appearance of spike potentials following illumination with bright light. These spikes, which do not appear in the normal fly retina, have a relatively long duration (20–50 ms), regenerative properties, and a rate of occurrence which increases with increasing light intensity. The spikes differed from the light response in being more susceptible to CO2 and to cuts in the eye. The spikes completely disappeared at low extracellular Ca2+ levels which did not reduce the amplitude of the light response. The spike potentials become triphasic when the recording electrode is advanced to the level of the basement membrane. This suggests that the spike potentials originate from the photoreceptor axons as a result of synchronous opening of voltage-dependent channels in a large number of photoreceptor cells. The occurrence of spike potentials during the process of degeneration was studied. Two phases can be distinguished: (1) Spike potentials appear in retinae of 2–3-day-old flies which display few morphological signs of degeneration. The frequency of appearance of spike potentials decreases in retinae of 14–16-day-old flies which show extensive degeneration of the R1–6 photoreceptor cells but no degeneration of the central R7,8 cells. (2) Spike potentials appear more frequently again in flies of 22–24 d of age. This is probably a consequence of degeneration of the remaining R7,8 photoreceptor cells. Temperature and the light-dark cycle had a critical effect on degeneration. Eight-day-old mutants raised at 19°C in a normal light-dark cycle showed only little degeneration. Eight-day-old mutants raised at 24°C showed only a slight degeneration when raised in the dark. However, the degree of degeneration was greatly enhanced in the mutants raised at 24°C under a light-dark cycle regime.The combined electrophysiological and morphological study of the degeneration, as a function of age and temperature, revealed that (1) the degeneration process takes place even in darkness, but at a slow rate, while light greatly accelerates the degeneration. (2) The degeneration is negligible at 19°C, even during light, in the first week after eclosion. (3) The appearance of spike potentials at an early stage of the degeneration suggests that changes in the plasma membrane of the photoreceptor cells manifest at an initial stage of the degeneration process.

scholarly journals An Electrogenic Sodium Pump in Limulus Ventral Photoreceptor Cells

1972 ◽  
Vol 59 (6) ◽  
pp. 720-733 ◽  
Author(s):  
J. E. Brown ◽  
J. E. Lisman
Keyword(s):  
Sodium Pump ◽  
Light Stimulus ◽  
Bright Light ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Intracellular Accumulation ◽  
Light Responses ◽  
Electrogenic Sodium Pump ◽  
Electrogenic Na Pump ◽  
Intracellular Ca

A hyperpolarization can be recorded intracellularly following either a single bright light stimulus or the intracellular injection of Na+. This after-hyperpolarization is abolished by bathing in 5 x 10-6 M strophanthidin or removal of extracellular K+. Both treatments also lead to a small, rapid depolarization of the dark-adapted cell. When either treatment is prolonged, light responses can still be elicited, although with repetitive stimuli the responses are slowly and progressively diminished in size. The rate of diminution is greater for higher values of [Ca++]out; with [Ca++]out = 0.1 mM, there is almost no progressive diminution of repetitive responses produced by either K+-free seawater or strophanthidin. We propose that an electrogenic Na+ pump contributes directly to dark-adapted membrane voltage and also generates the after-hyperpolarizations, but does not directly generate the receptor potential. Inhibition of this pump leads to intracellular accumulation of sodium ions, which in turn leads to an increase in intracellular Ca++ (provided there is sufficient extracellular Ca++). This increase in intracellular calcium probably accounts for the progressive decrease in the size of the receptor potential seen when the pump is inhibited.

scholarly journals Voltage-dependent K + channels improve the energy efficiency of signalling in blowfly photoreceptors

2017 ◽  
Vol 14 (129) ◽  
pp. 20160938 ◽  
Author(s):  
Francisco J. H. Heras ◽  
John Anderson ◽  
Simon B. Laughlin ◽  
Jeremy E. Niven
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Negative Feedback ◽  
Light Adaptation ◽  
Bright Light ◽  
Spiking Neurons ◽  
Delayed Rectifier ◽  
Voltage Response ◽  
Functional Requirements ◽  
Voltage Dependent

Voltage-dependent conductances in many spiking neurons are tuned to reduce action potential energy consumption, so improving the energy efficiency of spike coding. However, the contribution of voltage-dependent conductances to the energy efficiency of analogue coding, by graded potentials in dendrites and non-spiking neurons, remains unclear. We investigate the contribution of voltage-dependent conductances to the energy efficiency of analogue coding by modelling blowfly R1-6 photoreceptor membrane. Two voltage-dependent delayed rectifier K + conductances (DRs) shape the membrane's voltage response and contribute to light adaptation. They make two types of energy saving. By reducing membrane resistance upon depolarization they convert the cheap, low bandwidth membrane needed in dim light to the expensive high bandwidth membrane needed in bright light. This investment of energy in bandwidth according to functional requirements can halve daily energy consumption. Second, DRs produce negative feedback that reduces membrane impedance and increases bandwidth. This negative feedback allows an active membrane with DRs to consume at least 30% less energy than a passive membrane with the same capacitance and bandwidth. Voltage-dependent conductances in other non-spiking neurons, and in dendrites, might be organized to make similar savings.

Electrophysiology of the mammillary complex in vitro. II. Medial mammillary neurons

1992 ◽  
Vol 68 (4) ◽  
pp. 1321-1331 ◽  
Author(s):  
A. Alonso ◽  
R. R. Llinas
Keyword(s):  
Low Frequency ◽  
Input Resistance ◽  
Resting Potential ◽  
High Threshold ◽  
Potential Oscillations ◽  
Electrophysiological Properties ◽  
Voltage Dependent ◽  
Low Threshold ◽  
Membrane Potential Oscillations

1. The electrophysiological properties of guinea pig medial mammillary body (MMB) neurons were studied using an in vitro slice preparation. 2. The neurons (n = 80) had an average resting potential of -57 +/- 5.5 (SD) mV, an input resistance of 176 +/- 83 M omega, and a spike amplitude of 58 +/- 15.7 mV. Most of the neurons were silent at rest (n = 52), but some fired spontaneous single spikes (n = 16) or spike bursts (n = 14). 3. The main electrophysiological characteristic of MMB neurons was the ability to generate Ca(2+)-dependent regenerative events, which resulted in very robust burst responses. However, this regenerative event was not the same for all neurons, ranging from typical low-threshold Ca2+ spikes (LTSs) to intermediate-threshold plateau potentials (ITPs). 4. The ITPs were distinct from the LTSs in that they lasted > or = 100 ms and were not inactivated at membrane potentials at or positive to -55 mV. 5. Some cells with a prominent ITP and no LTS (n = 36) displayed repetitive, usually rhythmic, bursting (n = 14). This ITP could be powerful enough to maintain rhythmic membrane potential oscillations after pharmacological block of Na+ conductances. 6. A group of 32 MMB neurons displayed complex bursting that was generated by activation of both LTSs and ITPs. This was established on the basis of their distinct time- and voltage-dependent characteristics. In a group of neurons (n = 14), the burst responses were exclusively generated by an LTS; however, a Ca(2+)-dependent plateau potential contributed to the generation of rebound-triggered oscillatory firing. 7. In addition to the Ca(2+)-dependent LTS and/or ITP, MMB neurons always displayed high-threshold Ca2+ spikes after reduction of K+ conductances with tetraethylammonium. 8. MMB neurons display one of the richer varieties of voltage-dependent Ca2+ conductances so far encountered in mammalian CNS. We propose that the very prominent endogenous bursting and oscillatory properties of MB neurons allow this nuclear complex to function as an oscillatory relay for the transmission of low-frequency rhythmic activities throughout the limbic circuit.

scholarly journals Changes in Intracellular Free Calcium Concentration during Illumination of Invertebrate Photoreceptors

1974 ◽  
Vol 64 (6) ◽  
pp. 643-665 ◽  
Author(s):  
J. E. Brown ◽  
J. R. Blinks
Keyword(s):  
Light Adaptation ◽  
Light Stimulus ◽  
Electrical Response ◽  
Bright Light ◽  
Photoreceptor Cells ◽  
Ion Concentration ◽  
Free Calcium ◽  
Undetectable Level ◽  
Sequence Of Events ◽  
Intracellular Calcium Ion

Aequorin, which luminesces in the presence of calcium, was injected into photoreceptor cells of Limulus ventral eye. A bright light stimulus elicited a large increase in aequorin luminescence, the aequorin response, indicating a rise of intracellular calcium ion concentration, Cai. The aequorin response reached a maximum after the peak of the electrical response of the photoreceptor, decayed during a prolonged stimulus, and returned to an undetectable level in the dark. Reduction of Cao reduced the amplitude of the aequorin response by a factor no greater than 3. Raising Cao increased the amplitude of the aequorin response. The aequorin response became smaller when membrane voltage was clamped to successively more positive values. These results indicate that the stimulus-induced rise of Cai may be due in part to a light-induced influx of Ca and in part to release of Ca from an intracellular store. Our findings are consistent with the hypothesis that a rise in Cai is a step in the sequence of events underlying light-adaptation in Limulus ventral photoreceptors. Aequorin was also injected into photoreceptors of Balanus. The aequorin responses were similar to those recorded from Limulus cells in all but two ways: (a) A large sustained aequorin luminescence was measured during a prolonged stimulus, and (b) removal of extracellular calcium reduced the aequorin response to an undetectable level.

scholarly journals Electrophysiological Properties of Crayfish Retinal Photoreceptors

1990 ◽  
Vol 150 (1) ◽  
pp. 111-122
Author(s):  
ARTURO PICONES ◽  
HUGO ARÉCHIGA
Keyword(s):  
Time Course ◽  
Membrane Conductance ◽  
Light Response ◽  
Receptor Potential ◽  
Input Resistance ◽  
Resting Potential ◽  
Electrophysiological Properties ◽  
A Value ◽  
Retinal Photoreceptors ◽  
Conductance Increase

Electrical properties of crayfish retinular photoreceptors were studied in the dark-adapted state and during responses to light. In fully dark-adapted photoreceptors, the resting potential was −49.8±3.3mV and input resistance was 31.3±5.4MΩ (mean±S.E.). The current—voltage relationship showed rectification near the resting potential, with decreased resistance within the depolarizing range. A value of 29.8±5.0kΩcm2 was calculated for specific resistance, and 3.0±0.4μFcm−2 for specific capacitance. Electrotonic analysis showed that the photoreceptor was isopotential. During the light response, membrane conductance increased depending on the stimulus intensity. This relationship was steeper for the conductance change during the initial transient of the receptor potential than during the plateau. A depolarizing afterpotential usually ensued at the end of the light response, concurrent with a residual increased conductance. The time course of the conductance increase during the receptor potential showed two kinetic components, suggesting that at least two distinct membrane processes were involved in its generation.

scholarly journals A model of on/off transitions in neurons of the deep cerebellar nuclei: deciphering the underlying ionic mechanisms

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hugues Berry ◽  
Stéphane Genet
Keyword(s):  
Cerebellar Nuclei ◽  
Biophysical Model ◽  
High Threshold ◽  
Deep Cerebellar Nuclei ◽  
Functional Link ◽  
Electrophysiological Properties ◽  
Voltage Dependent ◽  
Ionic Mechanisms ◽  
The Central Nervous System ◽  
Overall Functioning

AbstractThe neurons of the deep cerebellar nuclei (DCNn) represent the main functional link between the cerebellar cortex and the rest of the central nervous system. Therefore, understanding the electrophysiological properties of DCNn is of fundamental importance to understand the overall functioning of the cerebellum. Experimental data suggest that DCNn can reversibly switch between two states: the firing of spikes (F state) and a stable depolarized state (SD state). We introduce a new biophysical model of the DCNn membrane electro-responsiveness to investigate how the interplay between the documented conductances identified in DCNn give rise to these states. In the model, the F state emerges as an isola of limit cycles, i.e. a closed loop of periodic solutions disconnected from the branch of SD fixed points. This bifurcation structure endows the model with the ability to reproduce the $\text{F}\to \text{SD}$ F → SD transition triggered by hyperpolarizing current pulses. The model also reproduces the $\text{F}\to \text{SD}$ F → SD transition induced by blocking Ca currents and ascribes this transition to the blocking of the high-threshold Ca current. The model suggests that intracellular current injections can trigger fully reversible $\text{F}\leftrightarrow \text{SD}$ F ↔ SD transitions. Investigation of low-dimension reduced models suggests that the voltage-dependent Na current is prominent for these dynamical features. Finally, simulations of the model suggest that physiological synaptic inputs may trigger $\text{F}\leftrightarrow \text{SD}$ F ↔ SD transitions. These transitions could explain the puzzling observation of positively correlated activities of connected Purkinje cells and DCNn despite the former inhibit the latter.

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