Dark-adaptation of the aspartate-isolated rod receptor potential of the frog retina: threshold measurements.

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.

• 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)

Chemical References

• Aspartic Acid
• Rhodopsin

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