Concentrations of biogenic amines in fundal layers in chickens with normal visual experience, deprivation, and after reserpine application

Abstract

Previous experiments in chickens have shown that dopamine released from the retina may be one of the messengers controlling the growth of the underlying sclera. It is also possible, however, that the apparent relationship between dopamine and myopia is secondary and artifactual. We have done experiments to assess this hypothesis. Using High Pressure Liquid Chromatography with electrochemical detection (HPLC-ED), we have asked whether changes in dopamine metabolism are restricted to the local retinal regions in which myopia was locally induced. Furthermore, we have measured the concentrations of biogenic amines separately in different fundal layers (vitreous, retina, choroid, and sclera) to find out how changes induced by “deprivation” (= removal of high spatial frequencies from the retinal image by translucent eye occluders which produce “deprivation myopia”) are transmitted through these layers. Finally, we have repeated the deprivation experiments after intravitreal application of the irreversible dopamine re-uptake blocker reserpine to see how suppression of dopaminergic transmission affects these changes. We found that (1) Alterations in retinal dopamine metabolism were indeed restricted to the retinal areas in which myopia was induced. (2) The retina was the major source of dopamine release with a steep gradient both to the vitreal and choroidal side. Vitreal content was about one-tenth, choroidal content about one-third, and scleral content about one-twentieth of that of the retina. (3) There was a drop by about 40% in vitreal dopamine, DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanilic acid) concentrations following deprivation which occurred already at a time where little changes could yet be seen in their total retinal contents. (4) Choroidal and scleral dopamine levels were not affected by deprivation, indicating that other messengers must relay the information to the sclera. (5) A single intravitreal injection of reserpine lowered dopamine and HVA levels in retina and vitreous for at least 10 days in a dose-dependent fashion and diminished or suppressed further effects of deprivation on these compounds. DOPAC levels continued to change upon deprivation even after reserpine injection (Fig. 3). Our results suggest that the release rates of dopamine from retinal amacrine cells can be estimated from vitreal dopamine concentrations; furthermore, they are in line with the hypothesis that there is an inverse relationship between dopamine release and axial eye growth rates. Although our experiments do not ultimately prove that dopamine has a functional role in the visual control of eye growth, they are in line with this notion.

Myopia-Inhibiting Concentrations of Muscarinic Receptor Antagonists Block Activation of Alpha2A-Adrenoceptors In Vitro

“…[74][75][76][77][78][79] Interestingly, both GABA and dopamine have been implicated in the regulation of eye growth. [80][81][82][83][84][85][86][87][88] In the rat retina, the epinephrine-synthesizing enzyme phenylethanolamine N-methyltransferase (PNMT) has been localized to amacrine cell populations 89 and retinal epinephrine levels have been reported to rise upon light exposure 90,91 ; but there is no further evidence for a role of epinephrine or norepinephrine in retinal visual processing of any vertebrate species examined. In spite of this, a-adrenoceptors are present on retinal neurons.…”

Dopamine D1 Receptors Contribute Critically to the Apomorphine-Induced Inhibition of Form-Deprivation Myopia in Mice

“…8 Furthermore, the decrease of retinal DOPAC was restricted only to the deprived area of the retina during partial deprivation. 9,10 In chickens, DOPAC recovered to normal levels after removal of the formdeprivation goggle. 11 Unlike FDM in chickens, recent studies showed that retinal dopamine levels remained unaltered in FDM C57BL/6 mice.…”

Vitamin D in Dry Eye and Myopia

“…More interestingly, studies using chicks also found that there was only reduction of DOPAC in the section of the deprived area in the retina and also only the deprived area grew further (Ohngemach et al, 1997;Stone et al, 2006). The results of the studies might be indicating that there is a negative association between retinal dopamine release and ocular growth, also the refraction can be affected via alteration of dopamine level results from deprived vision.…”

“…DOPAC was found to reduce in negative lens wearing chicks (Ohngemach et al, 1997). More interestingly, studies using chicks also found that there was only reduction of DOPAC in the section of the deprived area in the retina and also only the deprived area grew further (Ohngemach et al, 1997;Stone et al, 2006).…”

“…Investigations in other species such as tree shrew and guinea also demonstrated reduced dopamine levels in form deprived animals' retina (Dong et al, 2011a;McBrien et al, 2001). Because of large variability of dopamine levels between individuals, one could not firmly conclude there was a correlation between dopamine levels and myopia development until an inverted correlation between initial dopamine levels and the degree of deprivation myopia was shown (Ohngemach et al, 1997;Schaeffel et al, 1995). Recent studies have found that there is association between myopia development and time spending outdoors, for example, Jin and the colleague (2015) applied two 20-minute recess programs outside classroom during the day on school children between the age of 6 and 14…”