Current source-density analysis of the b-wave of frog retina.

Abstract

Current source-density analysis was used to study the spatial and temporal properties of b-wave current sources and sinks in the frog eye cup. The b-wave arises primarily from a current source near the retinal surface and from 2 current sinks, one in the distal portion of the inner plexiform layer and the other in the outer plexiform layer. The distal (outer plexiform layer) sink magnitude peaks at an earlier time than does the proximal sink, and decays at a faster rate. At early times the proximal sink is greater in magnitude. The currents of the proximal and distal sinks contribute positively to the transretinal voltage, summing to give the b-wave response. The spatial and temporal properties of the 2 current sinks closely match those of the 2 light-evoked extracellular K+ ([K+]o) increases. Increases in [K+]o apparently lead to the generation of b-wave currents. The distribution of these currents imply they flow through the glial cells of Mueller.