Figure 3. Fluo 5F fluorescence recorded from a salamander rod in 0 Ca²⁺, 0 Na⁺ solution in response to brief laser flashes.

A, dark-adapted rod was stepped to 0 Ca²⁺, 0 Na⁺ solution 1 s before a series of 5 laser flashes 100 ms in duration, separated by 5 s intervals. Laser intensity, 2.4 × 10¹⁰ photons μm⁻² s⁻¹. Fluorescence amplitudes to same laser flash protocol during a second exposure to 0 Ca²⁺, 0 Na⁺ solution after return to Ringer solution are indicated by the bars (Ped). B, same stimulus protocol as in A except that first laser pulse was omitted, so that the time between exposure to 0 Ca²⁺, 0 Na⁺ solution and the first laser flash was 6 s instead of 1 s.