title: The effects and interactions of GABAergic and dopaminergic agents in the prevention of form deprivation myopia by brief periods of normal vision.
abstract: Intravitreal injections of GABA antagonists, dopamine agonists and brief periods of normal vision have been shown separately to inhibit form-deprivation myopia (FDM). Our study had three aims: (i) establish whether GABAergic agents modify the myopia protective effect of normal vision, (ii) investigate the receptor sub-type specificity of any observed effect, and (iii) consider an interaction with the dopamine (DA) system. Prior to the period of normal vision GABAergic agents were applied either (i) individually, (ii) in combination with other GABAergic agents (an agonist with an antagonist), or (iii) in combination with DA agonists and antagonists. Water injections were given to groups not receiving drug treatments so that all experimental eyes received intravitreal injections. As shown previously, constant form-deprivation resulted in high myopia and when diffusers were removed for 2 h per day the period of normal vision greatly reduced the FDM that developed. GABA agonists inhibited the protective effect of normal vision whereas antagonists had the opposite effect. GABAA/C agonists and D2 DA antagonists when used in combination were additive in suppressing the protective effect of normal vision. A D2 DA agonist restored some of the protective effect of normal vision that was inhibited by a GABA agonist (muscimol). The protective effect of normal vision against form-deprivation is modifiable by both the GABAergic and DAergic pathways.
authors.affiliation: School of Optometry and Vision Science, Faculty of Health and Vision Improvement Domain, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Qld 4059, Australia. k.schmid@qut.edu.au
authors.forename: Katrina L
authors.initials: KL
authors.lastname: Schmid
authors.forename: Gal
authors.initials: G
authors.lastname: Strasberg
authors.forename: Cassie L
authors.initials: CL
authors.lastname: Rayner
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Hartfield
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D058452:Axial Length, Eye / Q000187:drug effects; D002645:Chickens; D015259:Dopamine Agents / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D004338:Drug Combinations; D004347:Drug Interactions; D005556:Form Perception; D018682:GABA Agents / Q000494:pharmacology*; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D058449:Intravitreal Injections; D008297:Male; D009216:Myopia / Q000209:etiology / Q000517:prevention & control*; D017448:Receptors, Dopamine D2 / Q000819:agonists; D018079:Receptors, GABA / Q000502:physiology; D011963:Receptors, GABA-A / Q000502:physiology; D018080:Receptors, GABA-B / Q000502:physiology; D042262:Retinoscopy; D012683:Sensory Deprivation; D014785:Vision, Ocular / Q000187:drug effects*
chemical_list: D015259:Dopamine Agents; D065127:Dopamine D2 Receptor Antagonists; D004338:Drug Combinations; D018682:GABA Agents; D018755:GABA Agonists; D018756:GABA Antagonists; C087200:GABA-C receptor; D017448:Receptors, Dopamine D2; D018079:Receptors, GABA; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B