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Yuval Cohen, IV, Edna Peleg, Michael Belkin, Uri Polat, Arieh S Solomon; The Dependency Between Vitreal Dopamine And Dihydroxyphenylacetic Acid (DOPAC) On Ambient Light Intensity. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6308.
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Light initiates a neuro-hormonal cascade that activates retinal amacrine cells to produce and release dopamine. Low luminance (3-80 lux) was shown to modify the accumulation and the release of dopamine in rats' retina (Brainard.,1987). Recently, we showed that ambient light that range from 50 to 10,000 lux modulates the development of chicks' refraction (Cohen., 2008, 2010). Since retinal dopamine is thought to be involved in the development of refraction, it is possible that its retinal concentration is modified by light intensity. The aim of the study was to examine the dependency between light intensity and vitreal dihydroxyphenylacetic acids (DOPAC) concentration that was shown to represent a more precise rate of retinal dopamine release (Megaw., 2001).
Male chicks (N=77) were exposed for 3 days to light intensity of 0, 50, 500, 10,000 lux at either continuous or 12h-/-12h light-dark cycles, with the light on at 7 am until 7 pm. The vitreous was extracted at 8 am and at 1 pm. Vitreal dopamine and DOPAC were quantified by liquid chromatography with electrochemical detection.
Light intensity modulates vitreal dopamine and DOPAC concentrations. Under continuous light, the mean diurnal DOPAC concentration of the high (10,000 lux)-, medium (500 lux)-, and low (50 lux)-intensity groups were 15.05±5.17, 8.55±2.1, 4.24±1.26 ng/ml, respectively (one-way ANOVA, P<0.0001). Under light-dark cycles, DOPAC concentration at 8 am and 1 pm were strongly correlated with light intensity (r=0.84, 0.72, respectively; P<0.0001). The mean diurnal DOPAC concentration was 2.7ng/ml greater in the high- vs. low-intensity groups. The peak vitreal dopamine concentration of the high- and low-intensity groups were 1.27±0.15 and 0.66±0.32 ng/ml, respectively (t-test, P=0.004).
Retinal dopamine release is dependent on ambient light intensity. Under light-dark cycle, retinal dopamine release showed significant variations according to light intensity. This study supports the hypothesis and provides a putative mechanism for the neuro-hormon dopamine involvement in the control of refractive development.
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