Intraretinal signaling by ganglion cell photoreceptors to dopaminergic amacrine neurons

Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):14181-6. doi: 10.1073/pnas.0803893105. Epub 2008 Sep 8.


Retinal dopaminergic amacrine neurons (DA neurons) play a central role in reconfiguring retinal function according to prevailing illumination conditions, yet the mechanisms by which light regulates their activity are poorly understood. We investigated the means by which sustained light responses are evoked in DA neurons. Sustained light responses were driven by cationic currents and persisted in vitro and in vivo in the presence of L-AP4, a blocker of retinal ON-bipolar cells. Several characteristics of these L-AP4-resistant light responses suggested that they were driven by melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs), including long latencies, marked poststimulus persistence, and a peak spectral sensitivity of 478 nm. Furthermore, sustained DA neuron light responses, but not transient DA neuron responses, persisted in rod/cone degenerate retinas, in which ipRGCs account for virtually all remaining retinal phototransduction. Thus, ganglion-cell photoreceptors provide excitatory drive to DA neurons, most likely by way of the coramification of their dendrites and the processes of DA neurons in the inner plexiform layer. This unprecedented centrifugal outflow of ganglion-cell signals within the retina provides a novel basis for the restructuring of retinal circuits by light.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amacrine Cells / metabolism*
  • Animals
  • Dopamine / metabolism*
  • Electrophysiology
  • Gene Expression Regulation
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Nerve Degeneration / metabolism
  • Patch-Clamp Techniques
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism
  • Retinal Ganglion Cells / metabolism*
  • Rod Opsins / metabolism
  • Signal Transduction*


  • Proto-Oncogene Proteins c-fos
  • Rod Opsins
  • melanopsin
  • Dopamine