Lateral spread of light-induced potentials along different cell layers in the teleost retina

Abstract

By displacing a spot of white light (0.25 mm in dia.), in steps of 0.25 mm along a straight line over the receptor surface, the extent of the lateral spread of light-induced potential recorded intracellularly and the related spike discharges were investigated in the isolated retina of fishes ( Gerridae, Centropomidae and Mugilidae). Hyperpolarizing S-potentials were found to spread laterally along each layer of horizontal cells and of a class of amacrine cells. The S-potential amplitude was maximal at the center of the light spot, and decayed to one half of its maximum when the light spot was displaced 0.5 to 1.5 mm away from the recording point; differences in the half decay distance along different horizontal and amacrine cell layers were statistically significant. In the inner plexiform layer, various types of light-induced (sustained or on-off transient) potentials were recorded intracellularly. Although some of these sustained potentials were C-type S-potentials, the others were assumed to arise from spike-producing cells. The lateral distribution of these potentials varied widely from cell to cell, and some of the sustained potentials showed polarity reversal with distance, from the central hyperpolarizing to the peripheral depolarizing response, or vice versa. The spatial changes observed in spike discharge pattern were closely related to the changes in the sustained potentials exhibiting the polarity reversal or in the depolarizing on-off transients.