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    This article has been cited by the following publications. This list is generated based on data provided by CrossRef.

    Lagnado, Leon and Schmitz, Frank 2015. Ribbon Synapses and Visual Processing in the Retina. Annual Review of Vision Science, Vol. 1, Issue. 1, p. 235.

    Van Hook, Matthew J. and Thoreson, Wallace B. 2014. Endogenous calcium buffering at photoreceptor synaptic terminals in salamander retina. Synapse, Vol. 68, Issue. 11, p. 518.

    Chen, Jeannie and Sampath, Alapakkam P. 2013. Retina.

    Molnar, Tünde Barabas, Peter Birnbaumer, Lutz Punzo, Claudio Kefalov, Vladimir and Križaj, David 2012. Store-operated channels regulate intracellular calcium in mammalian rods. The Journal of Physiology, Vol. 590, Issue. 15, p. 3465.

    Snellman, Josefin Mehta, Bhupesh Babai, Norbert Bartoletti, Theodore M Akmentin, Wendy Francis, Adam Matthews, Gary Thoreson, Wallace and Zenisek, David 2011. Acute destruction of the synaptic ribbon reveals a role for the ribbon in vesicle priming. Nature Neuroscience, Vol. 14, Issue. 9, p. 1135.

    Duncan, Gabriel Rabl, Katalin Gemp, Ian Heidelberger, Ruth and Thoreson, Wallace B. 2010. Quantitative Analysis of Synaptic Release at the Photoreceptor Synapse. Biophysical Journal, Vol. 98, Issue. 10, p. 2102.


Light regulation of Ca2+ in the cone photoreceptor synaptic terminal

  • DOI:
  • Published online: 01 September 2008

Retinal cones are depolarized in darkness, keeping voltage-gated Ca2+ channels open and sustaining exocytosis of synaptic vesicles. Light hyperpolarizes the membrane potential, closing Ca2+ channels and suppressing exocytosis. Here, we quantify the Ca2+ concentration in cone terminals, with Ca2+ indicator dyes. Two-photon ratiometric imaging of fura-2 shows that global Ca2+ averages ~360 nM in darkness and falls to ~190 nM in bright light. Depolarizing cones from their light to their dark membrane potential reveals hot spots of Ca2+ that co-label with a fluorescent probe for the synaptic ribbon protein ribeye, consistent with tight localization of Ca2+ channels near ribbons. Measurements with a low-affinity Ca2+ indicator show that the local Ca2+ concentration near the ribbon exceeds 4 μM in darkness. The high level of Ca2+ near the ribbon combined with previous estimates of the Ca2+ sensitivity of release leads to a predicted dark release rate that is much faster than observed, suggesting that the cone synapse operates in a maintained state of synaptic depression in darkness.

Corresponding author
*Address correspondence to: Richard H. Kramer, Department of Molecular and Cell Biology, University of California, 121 Life Sciences Addition, Berkeley, CA 94720-3200. E-mail:
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Visual Neuroscience
  • ISSN: 0952-5238
  • EISSN: 1469-8714
  • URL: /core/journals/visual-neuroscience
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