Generation of the e-wave of the electroretinogram in the frog retina

The e-wave and a delayed-OFF increase in extracellular K⁺ concentration are both maximum in the distal half of the inner plexiform layer. These responses also have similar latency, time-course, intensity-dependence, surround properties, and sensitivity to tetrodotoxin. Current source-density analysis of the e-wave reveals a current sink through the proximal retina, a source at the retinal surface, and, in some cases, a weaker source in the mid-retina. These results suggest a model for e-wave generation: delayed-OFF activity in proximal neurons releases K⁺, which enters Muller cells in the inner plexiform layer; a current exits Muller cells primarily via their endfeet, and the return flow through extracellular space produces the e-wave.