Interactions between ganglion cells in cat retina

Abstract

Cross-correlograms between simultaneously recorded Y-cells of the same center sign generally showed a fine structure, suggesting that the Y-cells had excitatory effects on each other. Interactions between ganglion cells were assessed directly by recording single ganglion cells intraocularly and activating one or more neighboring cells antidromically with electrical stimulation of the optic tract. The effect of one Y-cell on another was studied by locating one of the rare Y-cells > 7.degree. into the temporal retina that project contralaterally. With stimulation of the contralateral optic tract, this single, identified Y-cell was the only antidromically fired cell in the neighborhood, and its effects on neighboring cells were recorded. The antidromic firing of a single off Y-cell caused a sharp increase in the firing rate of any neighboring off Y-cell, starting within 0.5 ms and lasting 1.5 ms, and succeeded in firing an adjacent off Y-cell 1-4% of the time. Similarly, antidromic activation of a single on Y-cell excited neighboring on Y-cells. The antidromic firing of a single Y-cell had virtually no effect on neighboring Y-cells of the opposite center sign. The differing patterns of ipsilateral or contralateral projection for X- and Y-axons allowed a selective firing of either many X-cells and few Y-cells or many Y-cells and few or no X-cells. X-cells always had a brief excitatory effect on a Y-cell, X-cells usually had such an effect on an X-cell, and Y-cells seldom had an effect on an X-cell. An examination of the fine structure in correlations between simultaneously recorded ganglion cells provided evidence for interactions between cells in agreement with the results from stimulation. Interactions occurred always between Y-cells of the same center sign but never between Y-cells of opposite center sign. Interactions between neighboring X- and Y-cells or between neighboring X-cells were weaker than effects between Y-cells, occurred sporadically in .apprx. 12-24% of the pairs, and occurred between cells of the opposite as well as of the same center sign. The properties of the effects between ganglion cells suggest that the most likely mechanism is gap junctions between ganglion cells.