ROD AFTER-EFFECT IN S-POTENTIALS FROM CAT RETINA

The relation of the rod after-effect to per cent rhodopsin bleached was studied in S-potentials from cat retina. At threshold, flashes that produced the rod after-effect bleached only very small quantities of rhodopsin; and at a fixed flash duration, the duration of the after-effect increased as a function of log intensity. The after-effect's threshold occurred at about the intensity which saturated the maintained voltage. With flash intensity fixed (6.5 log td scotopic) and flash duration increased (0.5-64.0 sec) the duration of the after-effect was a linear function of exposure time. The duration continued to increase after an exposure of 16 sec, even though, at least 99 per cent of the rhodopsin had been bleached. It is concluded that the after-effect originates from something that accumulates after the maintained voltage in rod pathways reaches a ceiling. The accumulation can continue at a fixed rate irrespective of the bleaching rate. © 1969.