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J. Vicente, N. Forns, F. Germain, P. de la Villa; Functional Role of Intrinsically Photosensitive Retinal Ganglion Cells in Light Adaptation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):178.
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© ARVO (1962-2015); The Authors (2016-present)
To address the functional role of intrinsically photosensitive retinal ganglion cells (ipRGC) on the light adaptation.
By the use of electroretinogram (ERG) recordings on anaesthetized mice, we have tested the cone responses from living animals in animal groups under different day/night and dark/light conditions. We have also used circadian activity (CA) analysis to determine ipRGC sensitivity and ipRGC phase changing ability.
Our experiments demonstrate that ERG b-wave maximal amplitude of the cone response was significant higher when the animals were maintained under light adapted conditions, both in day or night phase of their circadian rhythm. Moreover, this effect of light adaptation was observed only when the intensity of the adaptation light source was enough to stimulate the ipRGC (≥ 200 cd•m-2). When mice were light adapted with a light source of such intensity not enough to stimulate the ipRGC (~10 cd•m-2), the amplitudes of the cone mediated b-wave were similar to those obtained under dark adapted conditions. In addition, CA studies in control and retinal degenerated animals established a photopic ipRGC sensitivity level as well as a possible functional connection between the ipRGC and dopaminergic amacrine cells.
From the present experiments we conclude that ipRGC are able to increase the light sensitivity of cone photoreceptors, thus showing an unknown mechanism of neural mediated light adaptation that can possibly involve the dopaminergic amacrine cells.
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