Fig. 2.

Time course of action of 8-Br-cAMP on response kinetics. A, Responses to 10 msec flashes recorded from a wild-type photoreceptor before, during (horizontal bar), and after application of 8-Br-cAMP (5 mm) from a puffer pipette placed near the recorded cell. Flashes were repeated, and responses were recorded at 20 sec intervals starting ∼2 min after establishing whole-cell configuration. Similar results were obtained on three other cells. Bottom, Changes in the values of time-to-peak (triangles) and current integrals (bars) of the macroscopic responses shown above. A gradual increase in the time-to-peak value was observed within 40 sec of 8-Br-cAMP application, with a partial recovery after washout. Although peak amplitudes decreased during application of cAMP, the current integral showed virtually no change. B, Individual macroscopic responses before (1), during (2), and after (3) 8-Br-cAMP application.