The organization of the outer plexiform layer in the retina of the cat: electron microscopic observations

The outer plexiform layer of the cat retina has been examined by electron microscopy of random and serial ultrathin sections in order that neural profiles might be positively identified and their synaptic relationships studied. Photoreceptors are interconnected by means of gap junctions as are the A horizontal cells. B horizontal cells and axon terminals do not appear to be engaged in any synapses apart from those with photoreceptors, while A horizontal cells make rare 'junctions' with cone bipolars only. Interplexiform cell processes probably account for all the conventional chemical synapses in the outer plexiform layer of cat retina.