An electrically evoked slow potential of the frog's retina. I. Properties of response

1. Brief pulses of electrical current passed through the frog's eye cup from sclera to vitreous (inward current) evoked large, vitreous positive slow potentials of retinal origin. Brief pulses of outward current evoke no response. 2. This electrically evoked retinal response (EERG) increased sharply in amplitude as the strength of the stimulus was increased. 3. Strength-duration curves showed that the stimulating pulse was integrated with a time constant ranging from 14 to 36 ms. The time constant was a function of the amplitude chosen as a criterion. 4. The EERG was abolished by chemical agents which abolish the PII component of the ERG (KCl, NH3, aspartate). 5. The waveform of the EERG returned to the base line with exactly the same time course as the PII component of the ERG, both when the PII was evoked by flashes of light and when it was evoked by flashes of darkness. 6. These results can be explained in terms of the hypothesis that electrical stimuli act on the synaptic terminals of the photoreceptor cells.