Some observations on the c-wave of the electroretinogram in the intact frog eye

The electroretinogram of the intact, circulated frog eye was recorded d.c. with a total drift of less than 100 μV/hr. The time to peak of the c-wave is linearly related to the log relative energy of a flash delivered to a dark-adapted eye over at least 4 decades. In response to a stepofillumination, a slow vitreal positivity develops until the d.c.-electroretinogram attains a plateau voltage. When the light is extinguished, the voltage falls slowly in the dark, possibly reflecting the regeneration of bleached rhodopsin. These slow voltage changes (shifts in the “standing potential”) share conditions in common with the c-wave, namely, they are present only under conditions of apposition between photoreceptors and pigment epithelium. It is suggested that the c-wave in the frog eye is the slowly-rising phase of the standing potential which decrements because the light has been extinguished. Simultaneous recordings of the d.c.-electroretinogram and single dimming fibres (class IV ganglion cells) show a close correlation between the c-wave and the activity of these units. Experiments are described in support of the hypothesis that the transretinal current flow generated by means of an interaction between photoreceptors and pigment epithelium can transmit through the retina information related to photoreceptor sensitivity.