Reactions of frog retinal rods to light

: The amplitude and shape of the rod photoresponses were investigated at different intensity, duration, wavelength and diameter of the light spot. Intracellular recordings were performed from the green and red rod outer sigments. An increase in the light intensity produced an increase in the amplitude and a decrease in the time rise of the response. An intensive light flash suppressed for a time the rod sensitivity to test flashes. At light spots of large diameter (100--1500 mum) delayed depolarizing deflection was observed. The latter was conditioned by illumination of receptor surroundings and, apparently, was due to horizontal cells activity. The possible role of the depolarizing effect of the rod surroundings illumination is discussed.