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L. Robbe, B.-A. Nguyen, A. Dorfman, M. Rufiange, J. Racine, S. Rosolen, P. Lachapelle; Uneven Contribution of the Oscillatory Potentials to the Genesis of the ERG Among Species. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1288.
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© ARVO (1962-2015); The Authors (2016-present)
When comparing the electroretinograms (ERG) obtained from different species one cannot escape noticing the fact that the oscillatory potentials (OPs) are major features in some species, such as the mouse, compared to others. We investigated if the prominence of the OPs on the ERG also meant an increased contribution of the OPs to the genesis of the ERG.
Luminance response function curves were obtained in scotopic (-6.3 to 0.6 log cd.sec.m-2) and photopic (0.9 log cd.sec.m-2, background: 30cd/m2) conditions from normal humans, guinea pigs (GPs), rats, and mice (n=4 per species). The ratio of the sum of OP amplitude/b-wave amplitude was calculated for each subject and group means were used to evaluate the OP contribution to the b-wave in each species.
The contribution of OPs to the photopic b-wave is equivalent (p>0.05) among humans, rats and mice (52.6%±2.3, 44.6%±3.5 and 50.4%±9.7, respectively), while it is significantly smaller (34%±5.2, p<0.05) in GPs. Interestingly, while the OP contribution to the scotopic b-wave in humans and rats remains unchanged (48.3%±1.8 and 46%±7.0, respectively; p<0.05) compared to that measured in photopic ERGs, the OPs contribution to the genesis of the scotopic ERG of mice and GPs increased significantly (69.4%±6.6 and 51.9%±7.8, p<0.05).
The contribution of the OPs to the genesis of the ERG is not uniform as it varies not only among species but also, in some species, with retinal adaptation. Given that OPs are thought to arise from amacrine cells, probably signalling the activation of an inhibitory feedback pathway, our results would suggest that these cellular mechanisms are differently modulated among species and/or retinal adaptation. This is most obvious when comparing rats and mice where rats do not demonstrate a significant enhancement in OP/b-wave ratio from photopic to scotopic while mice do (with the largest OP/b-wave ratio), suggesting that mice and rats may not be used as alternate, at least in studies where ERG and/or OPs are outcome variables.
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