scholarly journals Early Receptor Potentials of Rods and Cones in Rodents

1966 ◽  
Vol 49 (6) ◽  
pp. 1199-1208 ◽  
Author(s):  
WILLIAM L. PAK ◽  
THOMAS G. EBREY
Keyword(s):  
Time Course ◽  
Light Adaptation ◽  
Receptor Potential ◽  
Ground Squirrels ◽  
Wave Form ◽  
Second Phase ◽  
Response Curves ◽  
Early Receptor Potential ◽  
Time Courses ◽  
Cone Potential

The second phase (negative peak) of the early receptor potential of cones has been studied in the all-cone eyes of the Mexican and antelope ground squirrels (Citellus mexicanus and Citellus leucurus) and compared with responses from the rod-dominant eyes of the rat and flying squirrel (Glaucomys volans). The responses obtained from the all-cone eyes tended to be smaller in amplitude, to have higher thresholds, and to be considerably more resistant to light adaptation than the responses from the rod-dominant eyes. The wave forms and time courses of the two types of responses were similar, although the cone potential tended to be less sensitive to temperature variations and its time constants tended to be shorter than those of the rod potential. The spectral sensitivity of the second phase of the early receptor potential of the Mexican ground squirrel closely follows the absorption spectrum of a Dartnall nomogram pigment having its absorption maximum at 540 mμ. Moreover, as in the case of the rat, the amplitude of the response appears to be linearly related to the amount of pigment bleached in a flash. Thus, in both all-rod and all-cone systems the early receptor potential appears to arise in the photoexcitation of the respective visual pigment and appears to be closely linked to the initial photochemical events. The similarity of the wave form, time course, and stimulus-response curves in the two systems suggests that the early receptor potential is produced by similar mechanisms in all-rod and all-cone systems.

scholarly journals Adaptation in the Ventral Eye of Limulus is Functionally Independent of the Photochemical Cycle, Membrane Potential, and Membrane Resistance

1973 ◽  
Vol 61 (3) ◽  
pp. 273-289 ◽  
Author(s):  
A. Fein ◽  
R. D. DeVoe
Keyword(s):  
Membrane Potential ◽  
Time Constant ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Receptor Potential ◽  
Membrane Resistance ◽  
Initial Time ◽  
Early Receptor Potential ◽  
Time Courses ◽  
Sensitivity Changes

The early receptor potential (ERP), membrane potential, membrane resistance, and sensitivity were measured during light and/or dark adaptation in the ventral eye of Limulus. After a bright flash, the ERP amplitude recovered with a time constant of 100 ms, whereas the sensitivity recovered with an initial time constant of 20 s. When a strong adapting light was turned off, the recovery of membrane potential and of membrane resistance had time-courses similar to each other, and both recovered more rapidly than the sensitivity. The receptor depolarization was compared during dark adaptation after strong illumination and during light adaptation with weaker illumination; at equal sensitivities the cell was more depolarized during light adaptation than during dark adaptation. Finally, the waveforms of responses to flashes were compared during dark adaptation after strong illumination and during light adaptation with weaker illumination. At equal sensitivities (equal amplitude responses for identical flashes), the responses during light adaptation had faster time-courses than the responses during dark adaptation. Thus neither the photochemical cycle nor the membrane potential nor the membrane resistance is related to sensitivity changes during dark adaptation in the photoreceptors of the ventral eye. By elimination, these results imply that there are (unknown) intermediate process(es) responsible for adaptation interposed between the photochemical cycle and the electrical properties of the photoreceptor.

The Sensitivity of the Ventral Nerve Photoreceptor of Limulus Recovers after Light Adaptation in Two Phases of Dark Adaptation

1986 ◽  
Vol 41 (5-6) ◽  
pp. 657-667 ◽  
Author(s):  
I. Claßen-Linke ◽  
H. Stieve
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Light Flash ◽  
Light Response ◽  
Receptor Potential ◽  
Second Phase ◽  
Two Phases ◽  
Ventral Nerve Photoreceptor ◽  
External Calcium

The time course of the recovery of the sensitivity of the Limulus ventral nerve photoreceptor was measured during dark adaptation following light adaptation by a bright 1 or 5 s illumination. The stimulus intensity ICR of a 300 μs light flash evoking a response of criterion amplitude (receptor potential or receptor current under voltage clamp conditions) was used as measure of sensitivity.The time course of dark adaptation shows two phases with time constants in the range of 5-9 s and 300-500 s (15 °C). Only the first of the two phases is significantly changed when the extracel- lular Ca2+-concentration is varied.The power function ICR = a·Io-tDA-b gives a good data fit for each of the two phases of dark adaptation. In the first phase the factor ax and the exponent bx are decreased when the external calcium is lowered from 10 mmol/1 to 250 μmol/1. Conversely a1 and b1 are increased when the Ca2+-concentration is raised to 40 mmol/1. For the second phase neither a2 nor b2 is changed significantly upon the changes in calcium concentration in the same experiments.The two phases of dark adaptation reflect the behaviour of the two components C1 and C2 of the electrical light response (receptor potential or receptor current). Under the conditions described here C, determines the size of the light response during the first phase of dark adaptation whereas C2 mainly influences the size of the response during the second phase.Interpretation: The fast first phase of dark adaptation is determined by the change in intracellu- lar Ca2+-concentration. The slower second phase of dark adaptation is not primarily calcium- controlled.

scholarly journals Neurons, potassium, and glia in proximal retina of Necturus.

1980 ◽  
Vol 75 (2) ◽  
pp. 141-162 ◽  
Author(s):  
C J Karwoski ◽  
L M Proenza
Keyword(s):  
Time Course ◽  
Primary Source ◽  
Amacrine Cells ◽  
Müller Cell ◽  
Wave Form ◽  
Cell Responses ◽  
Decay Times ◽  
Low Pass ◽  
Muller Cell ◽  
Time Courses

Light-evoked K+ flux and intracellular Müller (glial) cell and on/off-neuron responses were recorded from the proximal retina of Necturus in eyecups from which the vitreous was not drained. On/off-responses, probably arising from amacrine cells, showed an initial transient and a sustained component that always exhibited surround antagonism. Müller cell responses were small but otherwise similar to those recorded in eyecups drained of vitreous. The proximal K+ increase and Müller cell responses had identical decay times, and on some occasions the latency and rise time of the K+ increase nearly matched Müller cell responses, indicating that the recorded K+ responses were not always appreciably degraded by electrode "dead space." The spatiotemporal distribution of the K+ increase showed that both diffusion and active reuptake play important roles in K+ clearance. The relationship between on/off-neuron responses and the K+ increase was modelled by assuming that (a) K+ release is positively related to the instantaneous amplitude of the neural response, and (b) K+ accumulating in extracellular space is cleared via mechanisms with approximately exponential time-courses. These two processes were approximated by low-pass filtering the on/off-neuron responses, resulting in modelled responses that match the wave form and time-course of the K+ increase and behave quantitatively like the K+ increase to changes in stimulus intensity and diameter. Thus, on/off-neurons are probably a primary source of the proximal light-evoked K+ increase that depolarizes glial cells to generate the M-wave.

Effect of External Calcium Concentration on the Intensity Dependence of Light-Induced Membrane Current and Voltage Signals in Two Defined States of Adaptation in the Photo-Receptor of Limulus

1986 ◽  
Vol 41 (11-12) ◽  
pp. 1092-1110 ◽  
Author(s):  
H. Stieve ◽  
H. Gaube ◽  
J. Klomfaß
Keyword(s):  
Stimulus Intensity ◽  
Time Course ◽  
Calcium Concentration ◽  
Light Adaptation ◽  
Receptor Potential ◽  
Membrane Current ◽  
Current Response ◽  
Current Signal ◽  
Intensity Dependence ◽  
Attenuation Function

Abstract The intensity dependence of the response of the Limulus ventral nerve photoreceptor to light flashes was determined in alternating measurements for the membrane current signal (receptor current) under voltage clamp conditions and the membrane voltage signal (receptor potential). Responses were obtained at two reproducible states of adaptation, while the photoreceptor was superfused by physiological saline (10 mmol/l Ca2+), or by salines with either lowered (250 μmol/l) or raised (40 mmol/l) calcium concentration. For the dark-adapted state of the photoreceptor the double logarithmic plot of the response current-time integral F (or the current amplitude) vs. flash intensity rises in a steep, supralinear section (slope 2-4) to a curve knee towards a less steep, sublinear section (slope 0.2-0.6), but does not reach saturation in the intensity range tested. Light adaptation shifts the response size vs. intensity curve towards higher light intensities. This sensitivity shift is enlarged in raised, and almost abolished in low external [Ca2+]. The changes of response latency and time-to-peak with stimulus intensity or adaptation are almost identical for receptor current and receptor potential. The decrease-time of the receptor current response, however, depends much less on the stimulus intensity or the state of adaptation than that of the receptor potential. The relative changes in the time course of the receptor current caused by light adaptation are not much influenced by variation of the [Ca2+]ex. Interpretation: The macroscopic receptor current signal consists of a volley of overlapping bumps; the size of these bumps is scaled by a calcium-dependent attenuation function which increases with delay time. This gradual growing attenuation a(t) acts as automatic gain control and may be responsible for the sublinear slope of the intensity dependence of the size of the receptor current. The supralinear slope of this dependence at lower stimulus intensities is probably caused by cooperative effects. Changes in the time course of the macroscopic receptor current due to light adaptation or varied calcium concentration are based on changes in the latency distribution of the underlying bump volley, and the size of the attenuation function.

scholarly journals Light-induced reduction in excitation efficiency in the trp mutant of Drosophila.

1982 ◽  
Vol 79 (3) ◽  
pp. 361-385 ◽  
Author(s):  
B Minke
Keyword(s):  
Rise Time ◽  
Transient Receptor Potential ◽  
Light Adaptation ◽  
Receptor Potential ◽  
Background Light ◽  
Excitation Efficiency ◽  
Early Receptor Potential ◽  
Intensity Response ◽  
Trp Mutant ◽  
Transient Receptor

In the transient receptor potential (trp) mutant of Drosophila, the receptor potential appears almost normal in response to a flash but quickly decays to baseline during prolonged illumination. Photometric and early receptor potential measurements of the pigment suggest that the pigment is normal and that the decay of the trp response during illumination does not arise from a reduction in the available photopigment molecules. However, there is reduction in pigment concentration with age. Light adaptation cannot account for the decay of the trp response during illumination: in normal Drosophila a dim background light shortens the latency and rise time of the response and also shifts the intensity response function (V-log I curve) to higher levels of light intensity with relatively little reduction in the maximal amplitude (Vmax) of response. In the trp mutant, a dim background light or short, strong adapting light paradoxically lengthens the latency and rise time of the response and substantially reduces Vmax without a pronounced shift of the V-log I curve along the I axis. The effect of adapting light on the latency and V-log I curve seen in trp are associated with a reduction in effective stimulus intensity (reduction in excitation efficiency) rather than with light adaptation. Removing extracellular Ca+2 reduces light adaptation in normal Drosophila, as evidenced by the appearance of "square" responses to strong illumination. In the trp mutant, removing extracellular Ca+2 does not prevent the decay of the response during illumination.

Effects of light-adaptation on the early receptor potential

1966 ◽  
Vol 6 (7-8) ◽  
pp. 357-371 ◽  
Author(s):  
G.B. Arden ◽  
Hisako Ikeda ◽  
I.M. Siegel
Keyword(s):  
Light Adaptation ◽  
Receptor Potential ◽  
Early Receptor Potential

scholarly journals Light-Induced Changes in Photoreceptor Membrane Resistance and Potential in Gecko Retinas

1974 ◽  
Vol 64 (1) ◽  
pp. 26-48 ◽  
Author(s):  
L. H. Pinto ◽  
W. L. Pak
Keyword(s):  
Time Course ◽  
Membrane Conductance ◽  
Receptor Potential ◽  
Membrane Resistance ◽  
Photoreceptor Membrane ◽  
Membrane Hyperpolarization ◽  
Direct Measurements ◽  
Isolated Retina ◽  
Time Courses ◽  
Induced Changes

The time-course of the light-induced changes in membrane voltage and resistance were measured for single photoreceptors in the retina of Gekko gekko. In the surgically isolated retina, small stimuli directed toward the impaled receptor produced a membrane hyperpolarization the time-course of which was identical to that of the increase in membrane resistance. In the eyecup preparation nearly identical time-courses were evoked only after perfusion of the vitreous surface with solution having high (Mg++). Disparate time-courses were obtained in (a) the isolated retina when large or displaced stimuli were used, and (b) the eyecup preparation when it was treated normally (see Pinto and Pak. 1974. J. Gen. Physiol. 64:49) and when it was exposed to aspartate ions or hypoxia. These results are consistent with the hypothesis that the receptor potential (elicited in the impaled receptor as a result of quanta only it captures) is generated by a single ionic process that decreases membrane conductance. These measurements provide a means to distinguish the receptor potential from interactions. From direct measurements of membrane time constant and total resistance in darkness, total membrane capacitance was calculated. The mean capacitance was 7.1 x 10-5 µF. This high value is consistent with anatomical observations of membrane infoldings at the base of gecko photoreceptors.

In the field mouse Mus booduga melatonin phase response curves (PRCs) have a different time course and wave form relative to light PRC

1999 ◽  
Vol 26 (3) ◽  
pp. 153-157 ◽  
Author(s):  
Vijay Kumar Sharma ◽  
Maroli K. Chandrashekaran ◽  
Muniyandi Singaravel ◽  
Ramanujam Subbaraj
Keyword(s):  
Time Course ◽  
Phase Response ◽  
Wave Form ◽  
Field Mouse ◽  
Response Curves ◽  
Phase Response Curves ◽  
Mus Booduga

scholarly journals Kinetics of Turn-offs of Frog Rod Phototransduction Cascade

2008 ◽  
Vol 132 (5) ◽  
pp. 587-604 ◽  
Author(s):  
Luba A. Astakhova ◽  
Michael L. Firsov ◽  
Victor I. Govardovskii
Keyword(s):  
Time Constant ◽  
Dark Current ◽  
Main Part ◽  
Time Course ◽  
Light Adaptation ◽  
Key Factors ◽  
Time Courses ◽  
Kinetics Of ◽  
Phototransduction Cascade ◽  
Effect Of Light

The time course of the light-induced activity of phototrandsuction effector enzyme cGMP-phosphodiesterase (PDE) is shaped by kinetics of rhodopsin and transducin shut-offs. The two processes are among the key factors that set the speed and sensitivity of the photoresponse and whose regulation contributes to light adaptation. The aim of this study was to determine time courses of flash-induced PDE activity in frog rods that were dark adapted or subjected to nonsaturating steady background illumination. PDE activity was computed from the responses recorded from solitary rods with the suction pipette technique in Ca2+-clamping solution. A flash applied in the dark-adapted state elicits a wave of PDE activity whose rising and decaying phases have characteristic times near 0.5 and 2 seconds, respectively. Nonsaturating steady background shortens both phases roughly to the same extent. The acceleration may exceed fivefold at the backgrounds that suppress ≈70% of the dark current. The time constant of the process that controls the recovery from super-saturating flashes (so-called dominant time constant) is adaptation independent and, hence, cannot be attributed to either of the processes that shape the main part of the PDE wave. We hypothesize that the dominant time constant in frog rods characterizes arrestin binding to rhodopsin partially inactivated by phosphorylation. A mathematical model of the cascade that considers two-stage rhodopsin quenching and transducin inactivation can mimic experimental PDE activity quite well. The effect of light adaptation on the PDE kinetics can be reproduced in the model by concomitant acceleration on both rhodopsin phosphorylation and transducin turn-off, but not by accelerated arrestin binding. This suggests that not only rhodopsin but also transducin shut-off is under adaptation control.

scholarly journals Ion permeation through light-activated channels in rhabdomeric photoreceptors. Role of divalent cations.

1996 ◽  
Vol 107 (6) ◽  
pp. 715-730 ◽  
Author(s):  
M D Gomez ◽  
E Nasi
Keyword(s):  
Time Course ◽  
Light Adaptation ◽  
Single Channel ◽  
Divalent Cations ◽  
Reversal Potential ◽  
Receptor Potential ◽  
Equilibrium Potential ◽  
Positive Equilibrium ◽  
Kinetics Of

The receptor potential of rhabdomeric photoreceptors is mediated primarily by a Na influx, but other ions must also permeate through light-dependent channels to account for some properties of the photoresponse. We examined ion conduction in macroscopic and single-channel light-induced currents of slug and scallop photoreceptors. In the absence of Na, a fivefold change in extracellular K shifted the reversal voltage of the photocurrent (Vrev) by approximately 27 mV. Because the dependency of Vrev on [K]o was sub-Nernstian, and Vrev in each condition was more positive than Ek, some other ion(s) with a positive equilibrium potential must be implicated, in addition to K. We assessed the participation of calcium, an important candidate because of its involvement in light adaptation. Three strategies were adopted to minimize the impairments to cytosolic Ca homeostasis and loss of responsiveness that normally result from the required ionic manipulations: (a) Internal dialysis with Na-free solutions, to prevent reverse operation of the Na/Ca exchanger. (b) Rapid solution changes, temporally limiting exposure to potentially detrimental ionic conditions. (c) Single-channel recording, exposing only the cell-attached patch of membrane to the test solutions. An inward whole-cell photocurrent could be measured with Ca as the only extracellular charge carrier. Decreasing the [Ca]o to 0.5 mM reduced the response by 43% and displaced the reversal potential by -4.3 mV; the shift was larger (delta Vrev = -44 mV) when intracellular permeant cations were also removed. In all cases, however, the current carried by Ca was < 5% of that measured with normal [Na]o. Unitary light-activated currents were reduced in a similar way when the pipette contained only divalent cations, indicating a substantial selectivity for Na over Ca. The fall kinetics of the photoresponse was slower when external Ca was replaced by Ba, or when the membrane was depolarized; however, dialysis with 10 mM BAPTA failed to antagonize this effect, suggesting that mechanisms other than the Ca influx participate in the modulation of the time course of the photocurrent.

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