Light peak of cat DC electroretinogram: not generated by a change in [K+]0

We have inquired whether a change in [K+]0 is associated in time with the light peak of the DC electroretinogram (ERG). If it is, this would implicate a change in [K+]0 as participating in the generation of the light peak. (The same response is usually recorded in humans by the the indirect technique of electro-oculography, giving the electro-oculogram (EOG).) Changes in [K+]0 were recorded with double-barrel, K+-specific microelectrodes from the retina and vitreous of the dark-adapted intact cat eye in response to maintained illumination. The light peak of the DC ERG was recorded from the reference barrel of the microelectrode when it was placed in the vitreous. No correlation was observed between the light peak and the changes in [K+]0 that were recorded in the retina or vitreous. We conclude that a retinal or vitreal change in [K+]0 is not directly involved in the mechanism that generates the light peak of the DC ERG.