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Two realms of dark adaptation
M L Firsov1, A V Kolesnikov, E Yu Golobokova
1Institute for Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez Prospect, 194223 St. Petersburg, Russia.
Vision Research
|December 8, 2004
Summary
Rod vision recovery slows significantly above 0.1% rhodopsin bleaching. Mathematical modeling reveals distinct phases of phototransduction recovery linked to specific rhodopsin photolysis products.
Area of Science:
- Vision science
- Photobiology
- Molecular biology
Background:
- Rod responsiveness recovery is crucial for vision.
- High levels of rhodopsin bleaching impair this recovery.
- Understanding the molecular mechanisms is key to visual adaptation.
Purpose of the Study:
- To mathematically describe the turn-off of the phototransduction cascade.
- To attribute specific recovery phases to rhodopsin photolysis products.
- To define the transition between light and dark adaptation.
Main Methods:
- Mathematical modeling of the phototransduction cascade.
- Analysis of rhodopsin photolysis and its products.
- Quantification of recovery phases (fast and slow).
Main Results:
- Recovery is retarded above a critical rhodopsin bleaching level (~0.1%).
- Fast recovery phase linked to metarhodopsin II and transducin quenching.
- Slow recovery phase controlled by inactivated metarhodopsins and rhodopsin regeneration.
Conclusions:
- Distinct molecular events govern fast and slow recovery phases.
- A critical bleaching threshold marks an abrupt transition in adaptation.
- This transition defines the boundary between light and dark adaptation reversal.