Adaptation is the modulation of the visual transduction process by prior illumination. Accordingly, its understanding depends on and contributes to understanding of the visual transduction process itself. Unfortunately, this mutual influence has not yet been very fruitful, perhaps because it calls for at least the beginnings of a complete model of the transduction process. Most of the work on adaptation, some highlights of which are reported here, have therefore been studies of the phenomenology of adaptation and of the chemicals which directly intermediate it. These studies are still largely groping in the dark, especially in vertebrates, and are therefore necessarily more tentative and less focussed than those of the transduction process itself, about which more is known. The formulation of open questions with which this report ends suggests, however, that the time has come when the state of our biochemical understanding of the transduction process (Chabre and Applebury and Applebury et al., both this volume) will make possible direct exploitation of the constraints imposed by adaptational data.
KeywordsHydrolysis Magnesium Depression Catalysis Titration
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