Direct rod input to cone BCs and direct cone input to rod BCs challenge the traditional view of mammalian BC circuitry

Proc Natl Acad Sci U S A. 2010 Jan 5;107(1):395-400. doi: 10.1073/pnas.0907178107. Epub 2009 Dec 14.


Bipolar cells are the central neurons of the retina that transmit visual signals from rod and cone photoreceptors to third-order neurons in the inner retina and the brain. A dogma set forth by early anatomical studies is that bipolar cells in mammalian retinas receive segregated rod/cone synaptic inputs (either from rods or from cones), and here, we present evidence that challenges this traditional view. By analyzing light-evoked cation currents from morphologically identified depolarizing bipolar cells (DBCs) in the wild-type and three pathway-specific knockout mice (rod transducin knockout [Tralpha(-/-)], connexin36 knockout [Cx36(-/-)], and transcription factor beta4 knockout [Bhlhb4(-/-)]), we show that a subpopulation of rod DBCs (DBC(R2)s) receives substantial input directly from cones and a subpopulation of cone DBCs (DBC(C1)s) receives substantial input directly from rods. These results provide evidence of the existence of functional rod-DBC(C) and cone-DBC(R) synaptic pathways in the mouse retina as well as the previously proposed rod hyperpolarizing bipolar-cells pathway. This is grounds for revising the mammalian rod/cone bipolar cell dogma.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Cell Shape
  • Connexins / genetics
  • Connexins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Patch-Clamp Techniques
  • Photic Stimulation
  • Retinal Bipolar Cells* / cytology
  • Retinal Bipolar Cells* / physiology
  • Retinal Cone Photoreceptor Cells / cytology
  • Retinal Cone Photoreceptor Cells / physiology*
  • Retinal Rod Photoreceptor Cells / cytology
  • Retinal Rod Photoreceptor Cells / physiology*
  • Synaptic Transmission / physiology
  • Transducin / genetics
  • Transducin / metabolism
  • Visual Pathways* / anatomy & histology
  • Visual Pathways* / physiology


  • Basic Helix-Loop-Helix Transcription Factors
  • Bhlhb4 protein, mouse
  • Connexins
  • connexin 36
  • Transducin