title: Inhibition of experimental myopia by a dopamine agonist: different effectiveness between form deprivation and hyperopic defocus in guinea pigs.
abstract: OBJECTIVE
  The dopamine (DA) system in the retina is critical to normal visual development as lack of retinal DA signaling may contribute to myopic development. The involvement of DA in myopic development is complex and may be different between form deprivation and hyperopic defocus. This study evaluated effects of a non-selective DA receptor agonist, apomorphine (APO) on refractive development in guinea pigs treated with form deprivation or hyperopic defocus.
  
  
  METHODS
  APO was subconjunctivally injected daily for 11 days in form-deprived (0.025 to 2.5 ng/µl) and defocused (0.025 to 250 ng/µl) eyes. Changes in ocular biometry and retinal concentration of DA and its metabolites (DOPAC) were measured in the 2 animal models to assess the level of DA involvement in each of the models (the less the change, the lower the involvement).
  
  
  RESULTS
  Similar myopic degree was induced in both the deprived and defocused eyes (-4.06 D versus -3.64 D) at 11 days of the experiment. DA and DOPAC levels were reduced in the deprived eyes but did not change significantly in the defocused eyes compared to the fellow and normal control eyes. A subconjunctival injection of APO daily for 11 days at concentrations ranged from 0.025 to 2.5 ng/µl inhibited form deprivation myopia in a concentration-dependent manner. By contrast, the APO treatment ranged from 0.025 to 250 ng/µl did not effectively inhibit the defocus-induced myopia and the associated axial elongation.
  
  
  CONCLUSIONS
  DA signaling may play a more critical role in form deprivation myopia than in defocus-induced myopia, raising a question whether the mechanisms of DA signaling are different under these two types of experimental myopia.
authors: School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China.
authors: Feng
authors: F
authors: Dong
authors: Zhina
authors: Z
authors: Zhi
authors: Miaozhen
authors: M
authors: Pan
authors: Ruozhong
authors: R
authors: Xie
authors: Xiaoyi
authors: X
authors: Qin
authors: Runxia
authors: R
authors: Lu
authors: Xinjie
authors: X
authors: Mao
authors: Jiang-Fan
authors: JF
authors: Chen
authors: Mark D P
authors: MD
authors: Willcox
authors: Jia
authors: J
authors: Qu
authors: Xiangtian
authors: X
authors: Zhou
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D001058:Apomorphine / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use; D001699:Biometry; D018491:Dopamine Agonists / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006956:Hyperopia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D056965:Injections, Intraocular; D023421:Models, Animal; D009216:Myopia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D011954:Receptors, Dopamine / Q000378:metabolism*; D012160:Retina / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D042262:Retinoscopy; D012683:Sensory Deprivation; D015398:Signal Transduction; D014785:Vision, Ocular; D014822:Vitreous Body / Q000187:drug effects*
chemical_list: D018491:Dopamine Agonists; D011954:Receptors, Dopamine; D015102:3,4-Dihydroxyphenylacetic Acid; D001058:Apomorphine