scholarly journals Fast electrical potentials arising from activation of metarhodopsin in the fly.

1980 ◽  
Vol 75 (4) ◽  
pp. 381-402 ◽  
Author(s):  
B Minke ◽  
K Kirschfeld
Keyword(s):  
Light Intensity ◽  
Receptor Potential ◽  
Second Order ◽  
Intracellular Recordings ◽  
M1 Phase ◽  
Cellular Origin ◽  
Electrical Potentials ◽  
Early Receptor Potential ◽  
Order Neuron

The cellular origin and properties of fast electrical potentials arising from activation of Calliphora photopigment were investigated. It was found by intracellular recordings that only the corneal-negative M1 phase of fly M potential arises in the photoreceptors' membrane. This M1 phase has all the accepted characteristics of an early receptor potential (ERP). It has no detectable latency, it survives fixation with glutaraldehyde, it is linear with light intensity below pigment saturation, and it is linear with the amount of metarhodopsin activated by light. The Calliphora ERP was found, however, to be exceptional because activation of rhodopsin, which causes the formation of metarhodopsin in 125 microsecond (25 degrees C), was not manifested in the ERP. Also, the extracellularly recorded ERP was not proportional to the rate of photopigment conversion. The corneal-positive M2 phase of the M potential was found to arise from second-order lamina neurons (L neurons). Intracellular recordings from these cells showed a fast hyperpolarizing potential, which preceded the normal hyperpolarizing transient of these cells. This fast potential appeared only when metarhodopsin was activated by a strong flash. The data indicate that the intracellularly recorded positive ERP, which arises from activation of metarhodoposin, elicits a hyperpolarizing fast potential in the second-order neuron. This potential is most likely the source of the corneal-positive M potential.

scholarly journals Properties of the pH-sensitive site that controls the lambda max of Limulus metarhodopsin.

1981 ◽  
Vol 77 (2) ◽  
pp. 191-203 ◽  
Author(s):  
J E Lisman ◽  
S Schulman ◽  
Y Sheline ◽  
P K Brown
Keyword(s):  
Intracellular Ph ◽  
Receptor Potential ◽  
Ph Sensitive ◽  
Phenol Red ◽  
Intracellular Recordings ◽  
Ph Buffering ◽  
Intracellular Injection ◽  
Early Receptor Potential ◽  
Sensitive Site ◽  
Secondary Result

A pH-sensitive site controls the lambda max of Limulus metarhodopsin. The properties of this site were examined using intracellular recordings of the early receptor potential (ERP) as a pigment assay. ERPs recorded over a range of extracellular pHs indicate that the apparent pK of the site is in the range of 8.3-8.6. Several lines of evidence indicate that the site responds directly to changes in extracellular pH (pHo) rather than to changes in intracellular pH(pHi) that follow as a secondary result of changing pHo : (a) the effect of changing pHo was rapid (less than 60 s); (b) when pHo was raised, the simultaneous rise in pHi, as measured with phenol red, was relatively small; (c) raising pHi by intracellular injection of pH 10 glycine buffer did not affect the site; and (d) the effect of changing pH0 could not be blocked by increasing the intracellular pH buffering capacity. It is concluded that the pH-sensitive site on metarhodopsin is on the extracellular surface of the plasma membrane.

scholarly journals Electrophysiological measurement of the number of rhodopsin molecules in single Limulus photoreceptors.

1977 ◽  
Vol 70 (5) ◽  
pp. 621-633 ◽  
Author(s):  
J E Lisman ◽  
H Bering
Keyword(s):  
Relative Intensity ◽  
Surface Density ◽  
Receptor Potential ◽  
Absolute Intensity ◽  
Charge Movement ◽  
Half Time ◽  
Quantal Response ◽  
Early Receptor Potential ◽  
Electrophysiological Measurement ◽  
Electrophysiological Methods

Two partly independent electrophysiological methods are described for measuring the number of rhodopsin molecules (R) in single ventral photoreceptors. Method 1 is based on measurements of the relative intensity required to elicit a quantal response and the relative intensity required to half-saturate the early receptor potential (ERP). Method 2 is based on measurements of the absolute intensity required to elicit a quantal response. Both methods give values of R approximately equal to 10(9). From these and other measurements, estimates are derived for the surface density of rhodopsin (8,000/micrometer2), the charge movement during the ERP per isomerized rhodopsin (20 X 10(-21) C), and the half-time for thermal isomerization of rhodopsin (36yr).

scholarly journals Retinal mechanisms of visual adaptation in the skate.

1975 ◽  
Vol 65 (4) ◽  
pp. 483-502 ◽  
Author(s):  
D G Green ◽  
J E Dowling ◽  
I M Siegel ◽  
H Ripps
Keyword(s):  
Ganglion Cell ◽  
Cell Activity ◽  
Receptor Potential ◽  
Visual Adaptation ◽  
Cell Discharge ◽  
Cell Responses ◽  
Electrical Potentials ◽  
Rate Of Recovery ◽  
Network Mechanism ◽  
Different Levels

Electrical potentials were recorded from different levels within the skate retina. Comparing the adaptive properties of the various responses revealed that the isolated receptor potential and the S-potential always exhibited similar changes in sensitivity, and that the b-wave and ganglion-cell thresholds acted in concert. However, the two sets of responses behaved differently under certain conditions. For example, a dimly iluminated background that had no measurable effect on the senitivities of either of the distal responses, raised significantly the thresholds of both the b-wave and the ganglion cell responses. In addition, the rate of recovery during the early, "neural" phase of dark adaptation was significantly faster for the receptor and S-potentials than for the b-wave or ganglion cell discharge. These results indicate that there is an adaptive ("network") mechanism in the retina which can influence significantly b-wave and gaglion cell activity and which behaves independently of the receptors and horizontal cells. We conclude that visual adaptation in the skate retina is regulated by a combination of receptoral and network mechanisms.

scholarly journals Enigma of early receptor potential in fly eyes

1989 ◽  
Vol 29 (12) ◽  
pp. 1663-1670 ◽  
Author(s):  
S. Gagné ◽  
J.G.H Roebroek ◽  
D.G. Stavenga
Keyword(s):  
Receptor Potential ◽  
Early Receptor Potential

The early receptor potential (ERP)

1987 ◽  
Vol 66 (1) ◽  
pp. 35-74 ◽  
Author(s):  
Winfried M�ller ◽  
Helmut T�pke
Keyword(s):  
Receptor Potential ◽  
Early Receptor Potential

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.

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