Abstract
Purpose:
Dopamine is involved in the development of myopia and the exact mechanism has not been fully clarified. One of our previous study showed that dopamine was involved in the progression of spontaneous myopia in albino guinea pigs under natural visual environments, probably due to a reciprocal action of the two dopamine receptors: activation of the D1 receptor and inhibition of the D2 receptor appear to prevent myopia. This study investigated whether this reciprocal action also plays a role in the development of form deprivation myopia (FDM) in pigmented guinea pigs (Cavia porcellus).
Methods:
Form deprivation was applied to pigmented guinea pigs (age: 2 weeks) that received daily peribulbar injection of SKF38393 (selective dopamine D1 receptor agonist) at doses of 10ng, 100ng, and 1000ng or quinpirole (selective dopamine D2 receptor agonist) at doses of 10ng, 33ng and 100ng for a period of 2 weeks. The refraction, corneal radius of curvature and axial components of the eye were measured in all animals prior to, at 1week and at 2 weeks of the experiments.
Results:
The D1 receptor agonist SKF38393 inhibited the development of FDM with the largest inhibition at a dose of 1000ng (-4.54±1.92D vs. -7.44±2.21D, p<0.05) followed by the dose of 100ng (-5.18±2.24D vs. -7.44±2.21D, p<0.05) at 2 weeks of experiments. The dose of 10ng of SKF38393 had no effect on FDM in wide type guinea pigs. In contrast, the D2 receptor agonist quinpirole promoted the development of FDM with dose dependent. The dose of 100ng had largest promotion of FDM (-10.05±3.02D vs.-6.86±2.39D, p<0.05) followed by the dose of 33ng (-8.87±2.62 D vs.-6.86±2.39D, p<0.05) at 2 weeks of experiments. The dose of 10ng of quinpirole had no effect on FDM.
Conclusions:
Our findings suggest that dopaminergic system regulates FDM development through the reciprocal activities of two type dopamine receptors in pigmented guinea pigs: D1 receptor activation inhibits, while D2 receptor activation promotes myopia.
Keywords: 605 myopia •
502 dopamine •
675 receptors: pharmacology/physiology