Pendrak K, Nguyen T, Lin T, Capehart C, Zhu X, Stone R A
Department of Ophthalmology, University of Pennsylvania, School of Medicine, Scheie Eye Institute, Philadelphia 19104-6075, USA.
Curr Eye Res. 1997 Feb;16(2):152-7. doi: 10.1076/ceyr.16.2.152.5090.
To address further a possible role for retinal dopamine in postnatal eye growth, we studied the response of retinal dopamine in eyes of chicks recovering from myopia.
Newborn chicks either received a unilateral translucent goggle to induce form deprivation myopia or were reared with unimpaired visual input. The goggle was removed from half of the chicks on day 7. Myopic, recovering and control never-goggled chicks were studied on days 7, 9 and 14. Eyes were enucleated postmortem and measured in axial and equatorial dimensions with calipers. Retinal levels of dopamine and its principal metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were assayed by high performance liquid chromatography with electrochemical detection.
Compared to contralateral and control eyes, retinas of goggled eyes at each time point had reduced levels of dopamine and DOPAC and a lowered calculated DOPAC/dopamine ratio, an index of dopamine metabolism. In eyes recovering from myopia, all biochemical parameters showed prominent increases by 2 days after goggle removal and had reached the level of both contralateral eyes and control eyes by one week after goggle removal. As evidence of a contralateral effect, the retinas of open eyes of chicks wearing a unilateral goggle demonstrated equal dopamine levels but reduced DOPAC compared to eyes of never-goggled chicks.
An early rise and eventual normalization of retinal dopamine, DOPAC and the DOPAC/dopamine ratio correlate with recovery from myopia. Combined with recent results from lens rearing experiments, these findings suggest that dopaminergic amacrine cells may participate in visually guided eye growth regulation and not just in the myopia response to visual form deprivation. The retinal biochemical alteration in eyes contralateral to a goggle identifies a previously unappreciated binocular interaction in the chick.
为进一步探讨视网膜多巴胺在出生后眼球生长中的可能作用，我们研究了近视恢复过程中小鸡眼睛中视网膜多巴胺的反应。
新生小鸡要么佩戴单侧半透明眼罩以诱发形觉剥夺性近视，要么在视觉输入未受损害的情况下饲养。在第7天，将一半小鸡的眼罩取下。在第7、9和14天对近视、恢复中的和未戴眼罩的对照小鸡进行研究。死后摘除眼球，用卡尺测量轴向和赤道尺寸。通过高效液相色谱电化学检测法测定视网膜中多巴胺及其主要代谢产物3,4-二羟基苯乙酸（DOPAC）的水平。
与对侧眼和对照眼相比，在每个时间点，戴眼罩眼的视网膜中多巴胺和DOPAC水平降低，计算出的DOPAC/多巴胺比值降低，该比值是多巴胺代谢的一个指标。在从近视恢复的眼睛中，所有生化参数在眼罩摘除后2天显著增加，并在眼罩摘除后一周达到对侧眼和对照眼的水平。作为对侧效应的证据，与未戴眼罩小鸡的眼睛相比，佩戴单侧眼罩小鸡的睁眼视网膜中多巴胺水平相等，但DOPAC降低。
视网膜多巴胺水平、DOPAC及其比值的早期升高及最终恢复正常与近视恢复相关。结合近期晶状体饲养实验的结果，这些发现表明多巴胺能无长突细胞可能参与视觉引导的眼球生长调节，而不仅仅参与对视觉形觉剥夺的近视反应。眼罩对侧眼的视网膜生化改变表明小鸡中存在一种以前未被认识的双眼相互作用。
