Abstract |
1. The dark-adaptation of the aspartate-isolated rod receptor potential of the isolated and perfused frog retina has been measured after bleaching about 5-10% of the rhodopsin. The fraction bleached (DeltaR) and the decay of rhodopsin photoproducts were determined using alternating measurements with a photometric technique (Donner & Hemilä, 1975).2. The dark-adaptation time course of the log threshold elevation is exponential, log I(t)/I(0) = W exp (-t/tau)+P, where W is the extrapolated value for log I(t)/I(0)-P at t = 0 and P is log I(t)/I(0) for t = infinity. When DeltaR increases from 2 to 10% W increases from ca. 2.6 to ca. 5. The time constant tau is about 13 min at 9 degrees C and 7 min at 14 degrees C (DeltaR = 5-10%).3. When the bleaching period is extended, keeping the amount bleached (Ixt) constant, dark-adaptation is completed earlier.4. The time course of dark-adaptation and the decay of the photoproduct ; retinal' are similar, as is also their dependence on temperature (Q(10) approximately 3).5. The permanent log threshold rise P is approximately proportional to DeltaR after small bleaches; when more than about 10% is bleached the slope of the curve P(DeltaR) decreases. P is considerably larger (about 2.5-fold) for the same fraction bleached in experiments at 14 degrees C as compared to experiments at 9 degrees C.6. A comparison with previously obtained corresponding values for dark-adaptation after small bleaches at the ganglion cell level shows a close agreement between the time constants for the dark-adaptation curve, its range and the dependence of threshold on the fraction of rhodopsin bleached.
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Authors | K O Donner, S O Hemilä |
Journal | The Journal of physiology
(J Physiol)
Vol. 287
Pg. 93-106
(Feb 1979)
ISSN: 0022-3751 [Print] England |
PMID | 311829
(Publication Type: Journal Article)
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Chemical References |
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Topics |
- Animals
- Anura
- Aspartic Acid
- Dark Adaptation
- In Vitro Techniques
- Kinetics
- Membrane Potentials
- Photoreceptor Cells
(physiology)
- Rana temporaria
- Regeneration
- Retina
(metabolism)
- Rhodopsin
(metabolism)
- Temperature
- Time Factors
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