title: An alternative pathway for signal flow from rod photoreceptors to ganglion cells in mammalian retina.
abstract: Rod signals in the mammalian retina are thought to reach ganglion cells over the circuit rod-->rod depolarizing bipolar cell-->AII amacrine cell-->cone bipolar cells-->ganglion cells. A possible alternative pathway involves gap junctions linking the rods and cones, the circuit being rod-->cone-->cone bipolar cells-->ganglion cells. It is not clear whether this second pathway indeed relays rod signals to ganglion cells. We studied signal flow in the isolated rabbit retina with a multielectrode array, which allows the activity of many identified ganglion cells to be observed simultaneously while the preparation is stimulated with light and/or exposed to drugs. When transmission between rods and rod depolarizing bipolar cells was blocked by the glutamate agonist 2-amino-4-phosphonobutyric acid (APB), rod input to all On-center and briskly responding Off-center ganglion cells was dramatically reduced as expected. Off responses persisted, however, in Off-center sluggish and On-Off direction-selective ganglion cells. Presumably these responses were generated by the alternative pathway involving rod-cone junctions. This APB-resistant pathway may carry the major rod input to Off-center sluggish and On-Off direction-selective ganglion cells.
mesh_terms: D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D002450:Cell Communication; D004307:Dose-Response Relationship, Radiation; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D066298:In Vitro Techniques; D008027:Light; D008954:Models, Biological; D011817:Rabbits; D012165:Retinal Ganglion Cells / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D014785:Vision, Ocular / Q000502:physiology
chemical_list: D000613:Aminobutyrates; D018690:Excitatory Amino Acid Agonists; C012729:2-amino-4-phosphonobutyric acid