Interreceptor junction in the double cone of the chicken retina

The two elements of the double cones in the chicken retina (Gallus gallus domesticus) are joined by a specialized junction located at the level of the myoid of the principal cone and the perikaryon of the accessory cone, in close proximity to the outer limiting membrane. In thin sections, the plasma membranes of the two elements of the cones are seen to approach each other closely being separated by a cleft of 3 to 11 nm; short gap junctions are interposed. A layer of fine filamentous material is constantly present on the cytoplasmic side of the plasma membranes. In replicas of freeze-fractured retinas the junction appears as a fascia composed of small polygonal gap junctions connected to one another by linear gap junctions. Solitary arrays of gap junctional particles are also present. In close proximity to the gap junctions the membrane matrix appears devoid of intramembrane particles. We conclude that the elements of the double cones are connected to one another by gap junctions with associated intermediate junction. The presence of gap junctions suggests that the two elements of the double cones are electrically coupled.