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Doc Ophthalmol (2012) 125:203209 DOI 10.1007/s10633-012-9347-9
ORIGINAL RESEARCH ARTICLE
Response properties of slow PIII in the Largevls mutant
Neal S. Peachey Gwen M. Sturgill-Short
Received: 27 June 2012 / Accepted: 23 July 2012 / Published online: 4 August 2012 Springer-Verlag (outside the USA) 2012
AbstractPurpose Mouse mutants for proteins expressed in the dystrophinglycoprotein complex at the photoreceptor terminal have electroretinogram (ERG) b-waves with a delayed onset and time course. The b-wave is dened by the sum of PII generated by depolarizing bipolar cells and slow PIII generated by Mller glial cells. In this study, we evaluated the hypothesis that the abnormalities observed in one of these mutants, Largevls, are caused by abnormal response properties of slow PIII.
Methods To isolate slow PIII, we crossed the Largevls mutant to a mouse line (Gpr179nob5) that lacks the ERG b-wave but maintains normal photoreceptor function and in which retinal degeneration does not occur. ERGs were recorded to strobe ash stimuli after overnight dark adaptation.
Results In comparison with control responses, the a-wave and slow PIII had comparable waveforms but
were reduced in amplitude in Largevls mice. The magnitude of this reduction was comparable for these components, and across stimulus luminance. There was no stimulus condition where the amplitude of slow PIII was larger than control.
Conclusions The data obtained are inconsistent with the idea that the b-wave abnormalities noted in Largevls mutant mice are caused by abnormal response properties of slow PIII.
Keywords B-wave Electroretinogram
Mller cell Slow PIII
Introduction
The electroretinogram (ERG) reects the algebraic summation of several underlying generators. In response to a strobe ash presented in darkness, the ERG is comprised of two main components, the a-wave and the b-wave. The a-wave reects the light-induced closure of sodium ion channels along the rod outer segment [1]. The positive polarity b-wave reects the summation of a positive polarity component (PII [2]) generated by rod depolarizing bipolar cells (DBCs [3]) and a negative polarity component (slow PIII) that reects Kir4.1 channel activity in Mller glial cells induced as a secondary response to light-evoked photoreceptor activity [37]. These underlying generators interact to dene
N. S. Peachey (&) G. M. Sturgill-Short
Louis Stokes Cleveland VA Medical Center, 10701 East Boulevard, Cleveland, OH 44106, USA e-mail: [email protected]
N. S. PeacheyCole...