Figure 2. Procedure for determining kinetics of the rising and falling phases of rod photoresponses to weak light flashes (the same cell as in Figure 1A). A: The rising phase of fractional responses recorded in Ringer’s solution (blue solid line, labeled “R”) and in the presence of 50-µM dopamine (red solid line, labeled “D”) after 20 min of exposure. The red dashed line shows the response in dopamine-containing solution scaled up by a factor of 1.27 to coincide with the response in Ringer’s solution. B: A single-exponential fit of the falling phase of fractional responses in Ringer’ solution (blue solid line, labeled “R”) and after 20 min incubation in 50-µM dopamine-containing solution (red solid line, labeled “D”). The turn-off time constants (τ_off) are shown near the curves of photoresponses.