An alternative pathway for signal flow from rod photoreceptors to ganglion cells in mammalian retina

Proc Natl Acad Sci U S A. 1995 Nov 7;92(23):10658-62. doi: 10.1073/pnas.92.23.10658.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aminobutyrates / pharmacology
  • Animals
  • Cell Communication*
  • Dose-Response Relationship, Radiation
  • Electrophysiology
  • Excitatory Amino Acid Agonists / pharmacology
  • In Vitro Techniques
  • Light
  • Models, Biological
  • Rabbits
  • Retinal Ganglion Cells / physiology*
  • Retinal Rod Photoreceptor Cells / drug effects
  • Retinal Rod Photoreceptor Cells / physiology*
  • Retinal Rod Photoreceptor Cells / radiation effects
  • Vision, Ocular / physiology


  • Aminobutyrates
  • Excitatory Amino Acid Agonists
  • 2-amino-4-phosphonobutyric acid