title: Variety of horizontal cell gap junctions in the rabbit retina.
abstract: In the rabbit retina, there are two types of horizontal cell (HC). The axonless A-type HCs form a coupled network via connexin 50 (Cx50) gap junctions in the outer plexiform layer (OPL). The axon-bearing B-type HCs form two independently coupled networks; the dendritic network via gap junctions consisted of unknown Cx and the axon terminal network via Cx57. The present study was conducted to examine the localization and morphological features of Cx50 and Cx57 gap junctions in rabbit HCs at cellular and subcellular levels. The results showed that each gap junction composed of Cx50 or Cx57 showed distinct features. The larger Cx50 gap junctions were located more proximally than the smaller Cx50 gap junctions. Both Cx50 plaques formed symmetrical homotypic gap junctions, but some small ones had an asymmetrical appearance, suggesting the presence of heterotypic gap junctions or hemichannels. In contrast, Cx57 gap junctions were found in the more distal part of the OPL but never on the axon terminal endings entering the rod spherules, and they were exclusively homotypic. Interestingly, about half of the Cx57 gap junctions appeared to be invaginated. These distinct features of Cx50 and Cx57 gap junctions show the variety of HC gap junctions and may provide insights into the function of different types of HCs.
authors.affiliation: Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
authors.forename: Jiook
authors.initials: J
authors.lastname: Cha
authors.forename: Hong-Lim
authors.initials: HL
authors.lastname: Kim
authors.forename: Feng
authors.initials: F
authors.lastname: Pan
authors.forename: Myung-Hoon
authors.initials: MH
authors.lastname: Chun
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Massey
authors.forename: In-Beom
authors.initials: IB
authors.lastname: Kim
mesh_terms: D000818:Animals; D017630:Connexins / Q000032:analysis*; D003712:Dendrites / Q000648:ultrastructure; D005136:Eye Proteins / Q000032:analysis*; D017629:Gap Junctions / Q000737:chemistry / Q000648:ultrastructure*; D016253:Microscopy, Immunoelectron; D017729:Presynaptic Terminals / Q000648:ultrastructure; D011817:Rabbits; D051248:Retinal Horizontal Cells / Q000648:ultrastructure*; D000099264:Connexin 50
chemical_list: D017630:Connexins; D005136:Eye Proteins; D000099264:Connexin 50