WHAT ARE THE MECHANISMS OF PHOTORECEPTOR ADAPTATION

This article evaluates each of the reactions known to be involved in v isual transduction as a potential site for the regulation of light ada ptation. Extensive evidence suggests that calcium acts as a feedback m essenger at several different points and recent work suggests a role f or cGMP in regulating the primary excitatory pathway. A conclusion is that adaptation is likely to be regulated by multiple and redundant me chanisms. The goal of future experimentation will be to determine the relative importance of each of these.