June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Assessment of Ca2+-permeable AMPA receptor calcium dynamics in ganglion cell layer neurons in an animal model of ocular hypertension
Author Affiliations & Notes
  • Elizabeth Cairns
    Pharmacology, Dalhousie University, Halifax, NS, Canada
  • Michele Archibald
    Physiology & Biophysics, Dalhousie University, Halifax, NS, Canada
  • Balwantray Chauhan
    Ophthalmology & Visual Sciences, Dalhousie University, Halifax, NS, Canada
    Physiology & Biophysics, Dalhousie University, Halifax, NS, Canada
  • Melanie Kelly
    Pharmacology, Dalhousie University, Halifax, NS, Canada
    Ophthalmology & Visual Sciences, Dalhousie University, Halifax, NS, Canada
  • William Baldridge
    Ophthalmology & Visual Sciences, Dalhousie University, Halifax, NS, Canada
    Anatomy & Neurobiology, Dalhousie University, Halifax, NS, Canada
  • Footnotes
    Commercial Relationships Elizabeth Cairns, None; Michele Archibald, None; Balwantray Chauhan, None; Melanie Kelly, None; William Baldridge, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 3407. doi:https://doi.org/
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Elizabeth Cairns, Michele Archibald, Balwantray Chauhan, Melanie Kelly, William Baldridge; Assessment of Ca2+-permeable AMPA receptor calcium dynamics in ganglion cell layer neurons in an animal model of ocular hypertension. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3407. doi: https://doi.org/.

      Download citation file:


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

      ×
  • Supplements
Abstract

Purpose: Glaucoma leads to loss of retinal ganglion cells (RGCs); however, the exact mechanisms leading to RGC death are not yet fully determined. One possible contributing mechanism is excessive influx of Ca2+ due to increased expression of Ca2+-permeable AMPA receptors (cpAMPARs). We examined this hypothesis by studying cpAMPAR-mediated Ca2+ dynamics in a rat model of ocular hypertension (OH).

Methods: OH was induced in 6 male Brown Norway rats by intraocular injection of polystyrene beads into the anterior chamber of one eye with the other eye serving as a control. Intraocular pressure (IOP) was measured with rebound tonometry. Retinas were harvested for imaging after 1-2 months of OH. AMPA-induced changes in ganglion cell layer neuron (GCN) intracellular calcium ([Ca2+]i) was quantified by fura-2, loaded into rat GCNs by electroporation, in isolated whole retina. The influence of cpAMPARs was assessed by comparing AMPA-induced (50 µM) increases of [Ca2+]i in the presence or absence of the cpAMPAR antagonist IEM-1460 (100 µM). To eliminate the confounding effects of NMDA receptors, all Ca2+-imaging experiments were performed in the presence of 20 µM MK-801. Following Ca2+ imaging the number of RGCs was subsequently assessed using immunohistochemistry for the RGC marker Brn3a.

Results: On average, OH rat eyes had a peak IOP increase (ΔIOP) of 16 ± 6 mm Hg (mean ± SD) and a 46% ± 19% loss of RGCs after 1-2 months compared to control (p<0.05, t-test). Calcium imaging of control eyes confirmed the presence of cpAMPARs in GCNs in that IEM-1460 decreased the AMPA-induced increase of fura-2 fluorescence to 47% (median, IQR 31%-70%; p<0.001, Friedman test and Dunn’s multiple comparison test; 111 cells from 5 retinas), an effect that was at least partially reversible (recovery to 75%, IQR 39%-99%) following 15 min wash. Similar results were found in GCNs from OH eyes: IEM-1460 decreased the AMPA-induced Ca2+ response to 48% (IQR 28%-79%, p<0.001, 110 cells from 6 retinas) with recovery to 66% (IQR 44%-100%) following wash.

Conclusions: The portion of the AMPA-induced [Ca2+]i increase blocked by IEM-1460 was similar in GCNs from eyes subjected to OH as compared fellow control eyes. This result is not consistent with an increased expression of cpAMPARs in GCNs in ocular hypertensive eyes.

Keywords: 439 calcium • 531 ganglion cells • 517 excitatory amino acid receptors  
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×