Adaptive properties of the b-wave and the PIII in the perfused isolated carp retina.

1. Perfusion of isolated carp retina with a pure oxygen saturated standard solution used in this experiment permitted several continuous hours of ERG recordings showing a distinctive b-wave as well as the PIII isolated by sodium aspartate. 2. The dark-adapted threshold for the PIII required an absorption of 5 to 6 quanta per rod. The 'rod-cone break' in the increment threshold curve for the b-wave was induced at a background intensity of about 2.0 X 10(-2) muW/cm2. 3. Both the b-wave and the PIII showed rapid and complete recovery of sensitivity after exposure to dim adapting lights. After bright light adaptation, the sensitivities went through a short 'fast phase' followed by a prolonged 'slow phase' of recovery. The rate of recovery during the fast phase was significantly faster for the PIII than for the b-wave. Neither a lowered temperature (9 degrees C) nor the application of ouabain (10(-6) M) influenced the fast phase. This seems to prove that the visual pigment, photoproducts and the active transport hardly participate in its mechanism, if at all. 4. The prolonged slow phase that followed the fast phase was distinguished by the recovery of the rod activity, even in isolated retinas.