June 2013
Volume 54, Issue 15
ARVO Annual Meeting Abstract  |   June 2013
CaV3.1 (T-Type) Calcium Channels in Bipolar Cells of the Macaque Retina
Author Affiliations & Notes
  • Theresa Puthussery
    Ophthal-Casey Eye Inst, Oregon Health & Science Univ, Portland, OR
  • Jacqueline Gayet
    Ophthal-Casey Eye Inst, Oregon Health & Science Univ, Portland, OR
  • William Taylor
    Ophthal-Casey Eye Inst, Oregon Health & Science Univ, Portland, OR
  • Footnotes
    Commercial Relationships Theresa Puthussery, None; Jacqueline Gayet, None; William Taylor, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 6158. doi:
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      Theresa Puthussery, Jacqueline Gayet, William Taylor; CaV3.1 (T-Type) Calcium Channels in Bipolar Cells of the Macaque Retina. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6158.

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

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Purpose: The functional properties of bipolar cells are shaped by the inventory and sub-cellular distribution of voltage-gated ion channels they express. Here, we examine the localization and functional expression of the T-type calcium channel subunit, CaV3.1, in bipolar cells of the macaque monkey retina.

Methods: Macaque eyes were obtained under the Tissue Distribution Program of the Oregon National Primate Research Center. For electrophysiology, whole-cell voltage-clamp and current-clamp recordings were made from bipolar cells in a light-adapted retinal slice preparation. For immunohistochemistry, paraformaldehyde fixed retinal sections were immunolabelled for CaV3.1 (Neuromab) in combination with subtype-specific bipolar cell markers.

Results: Depolarizing voltage steps from a holding potential of -90mV, revealed transient, mibefradil-sensitive, inward currents in cells that had morphological features consistent with DB2, DB4 and DB5 bipolar cells. In contrast, DB1, DB6 and midget bipolar cells lacked T-type currents. DB3 bipolar cells comprised two functionally distinct groups; one type, which we denote as DB3a, expressed large voltage-gated sodium currents but lacked T-type calcium currents, while a second type, which we denote as DB3b, exhibited large T-type calcium currents but lacked sodium currents. T-type currents remained in cells in which the axon terminal system had been removed, suggesting localization of channels in the somatic and/or dendritic compartments. Current-clamp recordings showed that T-type channels produce calcium spikes in response to depolarizing current injection. Immunohistochemistry for the T-type calcium channel subunit, CaV3.1, revealed expression in the somatodendritic compartment of the same bipolar cell types that exhibited T-type currents by electrophysiology.

Conclusions: These data demonstrate the presence of CaV3.1-mediated currents in sub-types of primate bipolar cells. We propose that these channels serve to boost signaling within transient visual pathways.

Keywords: 435 bipolar cells • 508 electrophysiology: non-clinical • 569 ion channels  

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