Horizontal-cell gap junction in the goldfish retina: area and density of particles as revealed by complementary freeze replicas.

Aiming at a morphological evaluation of horizontal cell gap junctions under intraocularly injected dopamine and 6-OH-dopamine influences as compared with those in the light and dark periods, the percentage of the junctional areas was computed by planimetry, and the distribution density of connexon particles by visual counting, on complementary freeze-replica electron micrographs. The outer plexiform layer was tentatively divided into the external-horizontal-somatic, intermediate-mixed-fibrous and internal-axon-terminal sublayers. The total number of connexon particles per cell seemed relatively unchanged, because the density of the particles was lower in the light period and after the dopamine treatment than in the dark and after the 6-OH-dopamine treatment; the percentage of the junctional area was conversely greater in the former than in the latter. The mode of response of the gap junction was presumed to occur in parallel with each of the sublayers after the chemical interference.