title: Effects of Constant Flickering Light on Refractive Status, 5-HT and 5-HT2A Receptor in Guinea Pigs.
abstract: OBJECTIVE
  To investigate the effects of constant flickering light on refractive development, the role of serotonin (i.e.5-hydroxytryptamine, 5-HT)and 5-HT2A receptor in myopia induced by flickering light in guinea pigs.
  
  
  METHODS
  Forty-five guinea pigs were randomly divided into three groups: control, form deprivation myopia (FDM) and flickering light induced myopia (FLM) groups(n = 15 for each group). The right eyes of the FDM group were covered with semitransparent hemispherical plastic shells serving as eye diffusers. Guinea pigs in FLM group were raised with illumination of a duty cycle of 50% at a flash frequency of 0.5Hz. The refractive status, axial length (AL), corneal radius of curvature(CRC) were measured by streak retinoscope, A-scan ultrasonography and keratometer, respectively. Ultramicroscopy images were taken by electron microscopy. The concentrations of 5-HTin the retina, vitreous body and retinal pigment epithelium (RPE) were assessed by high performance liquid chromatography, the retinal 5-HT2A receptor expression was evaluated by immunohistofluorescence and western blot.
  
  
  RESULTS
  The refraction of FDM and FLM eyes became myopic from some time point (the 4th week and the 6th week, respectively) in the course of the experiment, which was indicated by significantly decreased refraction and longer AL when compared with the controls (p<0.05). The concentrations of 5-HT in the retina, vitreous body and RPE of FDM and FLM eyes were significantly increased in comparison with those of control eyes (both p<0.05). Similar to FDM eyes, the expression of retinal 5-HT2A receptor in FLM eyes was significantly up-regulated compared to that of control eyes (both p<0.05). Western blot analysis showed that retinal 5-HT2A receptor level elevated less in the FLM eyes than that in the FDM eyes. Moreover, the levels of norepinephrine and epinephrine in FDM and FLM groups generally decreased when compared with control groups (all p<0.05).
  
  
  CONCLUSIONS
  Constant flickering light could cause progressive myopia in guinea pigs. 5-HT and 5-HT2A receptor increased both in form deprivation myopia and flickering light induced myopia, indicating that 5-HT possibly involved in myopic development via binding to5-HT2A receptor.
authors.affiliation: Central Laboratory, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Ophthalmology, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Xiumei
authors.initials: X
authors.lastname: Luo
authors.affiliation: Department of Ophthalmology, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.affiliation: Department of Ophthalmology, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Changyue
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Department of Ophthalmology, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Shunmei
authors.initials: S
authors.lastname: Ji
authors.affiliation: The State Key Laboratory of Medical Neurobiology, the Institutes of Brain Science and the Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Dermatology, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Shuangshuang
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Ophthalmology, Jinshan Hospital affiliated to Fudan University, Shanghai, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhou
mesh_terms: D000818:Animals; D006168:Guinea Pigs; D008027:Light / Q000009:adverse effects*; D008297:Male; D009216:Myopia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism*; D012029:Refraction, Ocular; D012160:Retina / Q000378:metabolism / Q000503:physiopathology / Q000528:radiation effects; D012701:Serotonin / Q000378:metabolism*
chemical_list: D044402:Receptor, Serotonin, 5-HT2A; D012701:Serotonin