GAP JUNCTIONS BETWEEN VISUAL CELLS IN THE SQUIRREL RETINA

Abstract

Visual cells in the squirrel (Tamius sibiricus) retina were studied by scanning and transmission electron microscopy to examine cell arrangement and occurrence of attachment structures between the visual cells. The squirrel retina, which was previously held to be a cone type, contained two types of visual cells: rods and cones. The two types were morphologically similar to their counterparts in other squirrel species. The two types of the visual cells occurred in a characteristic arrangement as a unit. The rods were sporadically distributed and each of them was surrounded by four to six cones. Gap junctions occurred at the level of the synaptic terminals of the visual cells. The gap junctions were formed between rods and cones, and between cones. However, no junctions were seen between rods. The rods were in contact with all the surrounding cones by gap junctions. The cones were in contact with one or two surrounding visual cells. Occurrence of the gap junctions between the visual cells was closely correlated with the unit-like arrangement of the visual cells. These findings suggest that a rod and its surrounding cones constitute a structural unit.