Altered Refractive Development in Mice With Reduced Levels of Retinal Dopamine

• Type of Material: Article
• Authors: Michael A. Bergen, Atlanta VA Medical Center; Han na Park, Emory University; Ranjay Chakraborty, Atlanta VA Medical Center; Erica G. Landis, Atlanta VA Medical Center; Curran Sidhu, Emory University; Li He, Emory University; Paul Iuvone, Emory University; Machelle Pardue, Emory University
• Language: English
• Date: 2016-08-01
• Publisher: Association for Research in Vision and Ophthalmology (ARVO)
• Publication Version: Final Published Version
• Copyright Statement: © 2016, Association for Research in Vision and Ophthalmology Inc.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1167/iovs.15-17784
• Title of Journal or Parent Work: Investigative Ophthalmology & Visual Science
• ISSN: 0146-0404
• Volume: 57
• Issue: 10
• Start Page: 4412
• End Page: 4419
• Grant/Funding Information: Supported by grants from the National Institutes of Health Grants R01EY016435, R01EY004864, P30EY006360 (Bethesda, MD, USA), Research Career Scientist Award (MTP) from the Department of Veterans Affairs Rehab R&D Service (Washington DC, USA), and an unrestricted departmental grant from Research to Prevent Blindness (New York, NY, USA).
• Keywords: EYE GROWTH; OCULAR GROWTH; Ophthalmology; C57BL/6 MOUSE; FORM-DEPRIVATION MYOPIA; AXIAL LENGTH; myopia; TREE SHREW; MOUSE MODEL; AMACRINE CELLS; refractive error; Science & Technology; KNOCKOUT MICE; Life Sciences & Biomedicine; OXYGEN-INDUCED RETINOPATHY; dopamine
• Research Categories: Health Sciences, Opthamology; Biology, Neuroscience

Abstract

Purpose: The neuromodulator dopamine (DA) has been implicated in the prevention of excessive ocular elongation and myopia in various animal models. This study used retina-specific DA knockout mice to investigate the role of retinal DA in refractive development and susceptibility to experimental myopia. Methods: Measurements of refractive error, corneal curvature, and ocular biometrics were obtained as a function of age for both untreated and form-deprived (FD) groups of retina-specific tyrosine hydroxylase knockout (rTHKO) and control (Ctrl) mice. Retinas from each group were analyzed by HPLC for levels of DA and its primary metabolite (DOPAC). Results: Under normal visual conditions, rTHKO mice showed significantly myopic refractions (F(1,188) = 7.602, P < 0.001) and steeper corneas (main effect of genotype F(1,180) = 5.1, P < 0.01) at 4 and 6 weeks of age compared with Ctrl mice. Retina-specific THKO mice also had thinner corneas (main effect of genotype F(1,181) = 37.17, P < 0.001), thinner retinas (F(6,181) = 6.07, P < 0.001), and shorter axial lengths (F(6,181) = 3.78, P < 0.01) than Ctrl mice. Retina-specific THKO retinas contained less than 15% of DA and DOPAC compared with Ctrl retinas, and the remaining DA had a significantly higher turnover, as indicated by DOPAC/DA ratios (Student's t-test, P < 0.05). Retina-specific THKO mice showed similar, yet more variable, responses to 6 weeks of FD compared with Ctrl mice. Conclusions: Diminished retinal DA induced spontaneous myopia in mice raised under laboratory conditions without form deprivation. The relative myopic shift in rTHKO mice may be explained by steeper corneas, an unexpected finding. The chronic loss of DA did not significantly alter the FD myopia response in rTHKO mice.