Melanopsin-expressing ganglion cells on macaque and human retinas form two morphologically distinct populations

Hsi Wen Liao, Xiaozhi Ren, Beth B. Peterson, David W. Marshak, King Wai Yau, Paul D. Gamlin, Dennis M. Dacey

Research output: Contribution to journalArticlepeer-review

81 Scopus citations


The long-term goal of this research is to understand how retinal ganglion cells that express the photopigment melanopsin, also known as OPN4, contribute to vision in humans and other primates. Here we report the results of anatomical studies using our polyclonal antibody specifically against human melanopsin that confirm and extend previous descriptions of melanopsin cells in primates. In macaque and human retina, two distinct populations of melanopsin cells were identified based on dendritic stratification in either the inner or the outer portion of the inner plexiform layer (IPL). Variation in dendritic field size and cell density with eccentricity was confirmed, and dendritic spines, a new feature of melanopsin cells, were described. The spines were the sites of input from DB6 diffuse bipolar cell axon terminals to the inner stratifying type of melanopsin cells. The outer stratifying melanopsin type received inputs from DB6 bipolar cells via a sparse outer axonal arbor. Outer stratifying melanopsin cells also received inputs from axon terminals of dopaminergic amacrine cells. On the outer stratifying melanopsin cells, ribbon synapses from bipolar cells and conventional synapses from amacrine cells were identified in electron microscopic immunolabeling experiments. Both inner and outer stratifying melanopsin cell types were retrogradely labeled following tracer injection in the lateral geniculate nucleus (LGN). In addition, a method for targeting melanopsin cells for intracellular injection using their intrinsic fluorescence was developed. This technique was used to demonstrate that melanopsin cells were tracer coupled to amacrine cells and would be applicable to electrophysiological experiments in the future. J. Comp. Neurol. 524:2845–2872, 2016.

Original languageEnglish (US)
Pages (from-to)2845-2872
Number of pages28
JournalJournal of Comparative Neurology
Issue number14
StatePublished - Oct 1 2016


  • RRID:AB_397181
  • amacrine cell
  • bipolar cell
  • dopamine
  • intrinsically photosensitive ganglion cell
  • primate retina

ASJC Scopus subject areas

  • General Neuroscience


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