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S. B. Varghese, E. E. Hartmann, J. C. Reid, K. T. Keyser; Effects of Nicotine on the Adult Electroretinogram (ERG). Invest. Ophthalmol. Vis. Sci. 2008;49(13):3807.
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To examine the effects of nicotine on information processing in the human retina by use of the ERG.
ERG responses were obtained from ten healthy non-smokers. All individuals were evaluated as visually normal on a comprehensive eye exam and visual field. Subjects were randomly assigned to one dosage of nicotine gum (2mg:n=4;4mg:n=6) and order of test session (placebo gum versus nicotine gum) was also randomized and masked. ERG responses were collected and analyzed using the Espion ERG system under standard ISCEV conditions. Responses were recorded from one eye for each subject using a Burien-Allen lens. Intensity response curves were obtained under both scotopic (1.41e-5-0.921 cd/m2) and photopic (0.283-35.84 cd/m2) conditions. The Naka-Rushton equation was used to fit the photopic stimulus-response series and paired student t-test was used for statistical analysis. All research reported was conducted in compliance with the Declaration of Helsinki.
The average subject age was 24.3 years (range=20-32yo). Means for coefficient of determination (R2 COD) of the Naka Rushton function, Vmax, and K for each condition are shown in the table below.Student t-test analysis of Vmax between the two nicotine dosage levels showed differences approaching significance (p=0.055). Absolute differences of Vmax between conditions (placebo versus nicotine) was also approaching significance (p=0.068).
The subjects displayed increases in b-wave peak amplitude responses under the influence of nicotine, with dose-related differences between the two concentrations of nicotine in the gum (2 vs.4 mg). The b-wave is considered to be primarily a measure of ON-bipolar cells and, therefore, these results are consistent with findings from animal studies that have identified α7 nicotinic acetylcholine receptors on ON cone bipolar cells. These data also corroborate previous studies of the effects of cholinergic agonists on ERG responses in cats that showed increases in photopic b-wave amplitude. To our knowledge, this is the first demonstration that nicotine affects retinal information processing in humans.
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