Melanopsin retinal ganglion cells receive bipolar and amacrine cell synapses

Michael A. Belenky, Cynthia A. Smeraski, Ignacio Provencio, Patricia J. Sollars, Gary E. Pickard

Research output: Contribution to journalArticlepeer-review

239 Scopus citations


Melanopsin is a novel opsin synthesized in a small subset of retinal ganglion cells. Ganglion cells expressing melanopsin are capable of depolarizing in response to light in the absence of rod or cone input and are thus intrinsically light sensitive. Melanopsin ganglion cells convey information regarding general levels of environmental illumination to the suprachiasmatic nucleus, the intergeniculate leaflet, and the pretectum. Typically, retinal ganglion cells communicate information to central visual structures by receiving input from retinal photoreceptors via bipolar and amacrine cells. Because melanopsin ganglion cells do not require synaptic input to generate light-induced signals, these cells need not receive synapses from other neurons in the retina. In this study, we examined the ultrastructure of melanopsin ganglion cells in the mouse retina to determine the type (if any) of synaptic input these cells receive. Melanopsin immunoreaction product was associated primarily with the plasma membrane of (1) perikarya in the ganglion cell layer, (2) dendritic processes in the inner plexiform layer (IPL), and (3) axons in the optic fiber layer. Melanopsin-immunoreactive dendrites in the inner (ON) region of the IPL were postsynaptic to bipolar and amacrine terminals, whereas melanopsin dendrites stratifying in the outer (OFF) region of the IPL received only amacrine terminals. These observations suggested that rod and/or cone signals may be capable of modifying the intrinsic light response in melanopsin-expressing retinal ganglion cells.

Original languageEnglish
Pages (from-to)380-393
Number of pages14
JournalJournal of Comparative Neurology
Issue number3
StatePublished - 2 Jun 2003
Externally publishedYes


FundersFunder number
National Institute of Mental HealthR01MH062296


    • Circadian rhythm
    • Intergeniculate leaflet
    • Pretectum
    • Retinohypothalamic tract
    • Suprachiasmatic nucleus


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