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A. Polosukhina, T. Huang, I. Tochitsky, Y. Sychev, D. Trauner, R. Van Gelder, R. Kramer; Restoring Light Sensitivity in Blind Mouse Retinas With an AAQ Photoswitch Molecule. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3469.
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© ARVO (1962-2015); The Authors (2016-present)
Retinitis pigmentosa (RP) is an inherited neurological disease that leads to blindness due to the progressive loss of rod and cone photoreceptors. We have developed a photochemical approach that ultimately might provide a treatment for RP and other retinal degenerative diseases. We are using acrylamide-azobenzene-quaternary-ammonium (AAQ), a photoisomerizable molecule that bestows light sensitivity onto endogenous voltage-gated K+ (Kv) channels. We evaluated whether AAQ could restore light sensitivity to retinas from mice with mutations that lead to blindness.
We applied AAQ (300 uM) onto flat-mount retinas from 6 month rd1 mice. After 25 minute treatment, AAQ was washed away. We performed electrophysiological recordings before and after a 25 minute treatment with AAQ. We used the whole-cell patch clamp method to evaluate ionic currents regulated by light in single retinal ganglion cells (RGCs) and a multielectrode array (MEA) to record from populations of RGCs. To investigate behavioral restoration of light sensitivity, we injected AAQ into the vitreous, and measured the pupillary reflex in the triple knockout mice (tra-/-,cnga3-/-,opn4-/- ) which normally fail to generate the reflex.
MEA recordings showed that retinas not treated with AAQ did not show light responses. However, after the AAQ treatment, consistently robust light responses were recorded from populations of RGCs. Whole-cell recordings from AAQ treated retinal ganglion cells (RGCs) show that we can directly control Kv currents with light. In addition to regulating intrinsic conductances, we have found that light regulates inhibitory and excitatory presynaptic neurons, amacrine and bipolar cells, respectively. We find that restoration of light sensitivity in retinal neurons leads to restoration of the pupillary reflex.
AAQ bestows light sensitivity onto multiple cell types, including amacrine, bipolar, and ganglion cells; consequently inducing light-evoked spiking activity in ganglion cells in blind retinas from rd1 mice. These results show that AAQ is a tool that restores visual sensitivity in retinal degenerative animal models and has the potential for future clinical applications.
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