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T. I. Tsai, B. V. Bui, A. J. Vingrys; Müller Cell Buffering of Potassium Ion Currents in the Rat Retina Influences the Generation of Visual Evoked Potentials. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5764.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the influence of retinal Müller cell mediated potassium buffering in the generation of visual evoked potentials (VEP).
Anaesthetised (Ketamine:Xylazine, 60:5 mg/kg) Long Evans rats (n = 5) were intravitreally injected into one eye with barium chloride (BaCl2, 2 µL, 2 mM), an inhibitor of Müller cell potassium channels. The fellow eye was sham-treated with vehicle and served as control. VEP control was the hemisphere ipsilateral to BaCl2 treatment. The ERG and VEP were acquired 30 minutes after injection (-5.93 to 1.55 log scotopic cd.s.m-2) from both eyes and both hemispheres simultaneously. ERGs were analysed for photoreceptoal (PIII), ON-bipolar cell (PII) and inner retinal responses (oscillatory potentials, OPs and the scotopic threshold response, STR). VEPs were analysed for the amplitude P1N1 and N1P2 as per convention.
Photoreceptor responses were unaffected by BaCl2 (PIII +8 ± 13%, p = 0.66), whereas the bipolar cell response (PII +132 ± 24%, p < 0.001) and inner retinal oscillations (OPs +158 ± 31%, p < 0.001) were enhanced. The STR was absent after BaCl2 treatment (-82 ± 6%, p < 0.01) indicating reduced retinal ganglion cell (RGC) output. VEPs were significantly reduced (P1N1 -70 ± 5% and N1P2 -66 ± 6%, both p < 0.001) with the remnant VEPs being not significantly different to that recorded under occlusion of the contralateral eye in a similar set of rats (P1N1 -73 ± 9% and N1P2 -73 ± 11%, p = 0.40 and 0.10, respectively).
BaCl2-sensitive components contribute to the PII and STR in rats. The absence of a retinal STR was associated with the loss of the VEP. This suggests that Müller cells potassium buffering is important for the ERG STR generation and transmission of signals from eye to the brain of rats.
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