HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Donner, K. O. Articles by Hemilä, S. O. Search for Related Content PubMed PubMed Citation Articles by Donner, K. O. Articles by Hemilä, S. O.

Department of Zoology, University of Helsinki, Helsinki 10, Finland

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 (R) 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/I₀ = W exp (-t/)+P, where W is the extrapolated value for log I_t/I₀-P at t = 0 and P is log I_t/I₀ for t = . When R increases from 2 to 10% W increases from ca. 2·6 to ca. 5. The time constant is about 13 min at 9 °C and 7 min at 14 °C (R = 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 (Q₁₀ 3).

5. The permanent log threshold rise P is approximately proportional to R after small bleaches; when more than about 10% is bleached the slope of the curve P(R) decreases. P is considerably larger (about 2·5-fold) for the same fraction bleached in experiments at 14 °C as compared to experiments at 9 °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.