May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Retinal Glial Cells Contribute Significantly to the Negative Erg Found in the mdxCv3 Duchenne Muscular Dystrophy Mouse
Author Affiliations & Notes
  • D.G. Green
    Ophthalmology, University MI–Kellogg Eye Ctr, Ann Arbor, MI
  • B.R. Pattnaik
    Ophthalmology, University MI–Kellogg Eye Ctr, Ann Arbor, MI
  • D.M. Pillers
    Pediatrics, Ophthalmology and Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR
  • Footnotes
    Commercial Relationships  D.G. Green, None; B.R. Pattnaik, None; D.M. Pillers, None.
  • Footnotes
    Support  NIH Grants EY10084 & EY07003, Research to Prevent Blindness, and the Foundation Fighting Blindness
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 5156. doi:
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      D.G. Green, B.R. Pattnaik, D.M. Pillers; Retinal Glial Cells Contribute Significantly to the Negative Erg Found in the mdxCv3 Duchenne Muscular Dystrophy Mouse . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5156.

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

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Abstract

Abstract: : Purpose: The mdxCv3 mouse has a deficiency in all carboxy–terminal dystrophin isoforms and is a good model for the retinal changes seen in Duchenne muscular dystrophy (DMD). These mice have a negative corneal ERG, reduced scotopic b–waves and increased b–wave implicit times. Recently, the distribution of the KIR4.1 inward rectifying potassium channels, the primary K+ channels in Müller cells, have been reported to be affected in mdxcv3 (Connors and Kofuji, 2002). To assess the extent to which the abnormalities in the ERG are related to the glial cell K+ channel changes, we have measured in vitro the effects of blocking inward rectifying channels with Ba2+. Methods: Pieces of dark–adapted retina from either mdxCv3 or C57BL/6J retinas were superfused with an oxygenated Ringer at 36–37 o C. Using two extracellular microelectrodes, one touching the tips of the photoreceptor outer segments and the other on the vitreal side of the retina, transretinal ERGs to flashes of light were recorded. The changes produced by adding 200 µM of Ba2+ to the perfusate were determined. Results: The ERGs from pieces of isolated mdxCv3 retina differed from those from isolated C57BL/6J retinas in that they were predominately negative, show reduced b–wave amplitudes, and increased b–wave implicit times. After Ba2+ was added to the perfusate, slow PIII was eliminated and the b–wave amplitude was increased. Moreover, the mdxCv3 ERG was no longer negative and appeared similiar to the wild type ERG. However the implicit time differences between mdxCv3 and the wild type ERG persisted. Conclusions:Ba2+ is known to block inward rectifying potassium channels on Müller cells. The ability of low concentrations of Ba2+ to block slow PIII and to convert the negative mdxCv3 ERG to one that is more normal in shape suggests that glial cell changes in mdxCv3 lead to an increased slow PIII which plays a major role in producing the negative ERG.

Keywords: electrophysiology: non–clinical • Muller cells • ion channels 
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