April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
Calcium-Induced Calcium Release Regulates Synaptic Release From Mouse Rods
Author Affiliations & Notes
  • N. Babai
    Ophthalmology and Visual Sciences, Univ of Nebraska Med Ctr, Omaha, Nebraska
  • C. W. Morgans
    Casey Eye Institute, Oregon Health & Science University, Oregon
  • W. B. Thoreson
    Ophthalmology and Visual Sciences, Univ of Nebraska Med Ctr, Omaha, Nebraska
  • Footnotes
    Commercial Relationships  N. Babai, None; C.W. Morgans, None; W.B. Thoreson, None.
  • Footnotes
    Support  NIH Grant EY10542 (WBT), Research to Prevent Blindness, NIH Grant EY014700 (CWM)
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 1007. doi:
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    • Get Citation

      N. Babai, C. W. Morgans, W. B. Thoreson; Calcium-Induced Calcium Release Regulates Synaptic Release From Mouse Rods. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1007.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Calcium-induced calcium release (CICR) boosts synaptic release from rods in amphibian retina. We tested whether CICR contributes to synaptic release from rods in mouse retina.

Methods: : Intraretinal ERGs were recorded from mouse eyecups. For confocal Ca2+ imaging, mouse retinal slices were loaded with Fluo4-AM. Whole cell recordings were obtained in retinal slices using ruptured and perforated patch techniques. For immunofluorescence confocal microscope, lightly fixed mouse retina sections were incubated with antibodies against SERCA2 and ribeye followed by fluorescent secondary antibodies.

Results: : Electron micrographs as well as immunofluorescent double labeling for the endoplasmic reticulum (ER) protein, SERCA2, and ribeye indicate a close association between the ER and synaptic ribbons in rod terminals. Stimulating CICR with 10 µM ryanodine evoked Ca2+ increases in rod terminals and membrane depolarization (N=7). Inhibiting CICR with a high concentration of ryanodine (100 µM) reduced the ERG b-wave but not a-wave consistent with inhibition of synaptic transmission (N=4). Ryanodine (100 µM) also inhibited light responses of individual RBCs (N=4) and presumptive horizontal cells (N=4). Inhibition of light responses in both types of second order neurons with different glutamate receptors suggests ryanodine acts presynaptically. Consistent with presynaptic effects, ryanodine (100 µM) did not alter simulated light responses of RBCs generated by puffing CPPG (600 µM) into the OPL while continuously perfusing L-AP4 (4 µM, N=6). Ryanodine (100 µM) inhibited outward currents in RBCs evoked by electrical stimulation of rods with electrodes among the outer segments (N=9). Electrically-evoked outward currents were also blocked by the mGluR6 agonist L-AP4 (4 µM, N=6) and antagonist CPPG (600 µM, N=5) indicating that currents are due to mGluR6 activation.

Keywords: retina: distal (photoreceptors, horizontal cells, bipolar cells) • calcium • photoreceptors 

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