Predicted kinetics of protein activation, of cGMP concentration, and of electrical current in response to a single photoisomerization when all inactivation reactions are ignored. The cGMP concentration and the circulating electrical current decline from their respective dark levels along trajectories that are approximately parabolic at early times. Both variables are plotted normalized to their dark levels, and the symbol F denotes the fraction of current remaining. The dotted trace allows for inactivation reactions. Estimation of amplification constant from a family of flash responses.
Continuous traces are experiments from another toad rod.