Specificity of Dopamine-2 Receptor Agonist on Eyeball Growth in Chicken Model of Myopia

ABSTRACT

The authors examined the specificity of the dopamine-2 receptor for eyeball growth of the experimental myopic chicken eyes. Two day-old white Leghorn chickens were monocularly deprived of vision by lid suture of the right eyes. We measured the axial lengths of chicken's eyes by ultrasonography at the 2nd day and the 4th weeks. The right eyes of the first group were instillated with 0.04cc of tris buffer solution, those of the second and third group were instillated with 0.04cc of 0.02% SKF38393 hydrochloride solution and 0.02% bromocriptine solution individually. All solutions were instillated into the right eyes two times per day during 4 weeks. At the 2nd day of the age, the axial lengths of the first group's eyeballs were 7.83 +/- 0.14mm in the right, 7.87 +/- 0.15mm in the left eyes, 7.78 +/- 0.16mm in the right eyes, 7.77 +/- 0.11mm in the left eyes of the second group and 7.89 +/- 0.12mm in the right eyes, 7.87 +/- 0.12mm in the left eyes of the third group. Each group was not statistically different (p>0.05). But at the four weeks of the age, the axial lengths of the lid sutured right chicken eyeball were 11.39 +/- 0.27mm in the first group, 11.40 +/- 0.40mm in the second group and 11.20 +/- 0.40mm in the third group, The third group was statistically different from the first or 2nd group (p<0.05). The growth of the axial lengths of the right chicken eyeballs from the 2nd day to the 4th week of the age was 3.50 +/- 0.35mm in the first, 3.63 +/- 0.42mm in the second and 3.21 +/- 0.29mm in the third group. The right eyes of the third group were found significantly less growth than those of other groups. These results suggest that dopamine-2 receptor playa role in eyeball growth.