[A study on the mechanism of apomorphine for treatment of myopia]

To investigate the functions of dopamine D(1) and D(2) receptor in form deprivation myopia (FDM) and the influence of apomorphine (Apo) on inhibition of FDM in chick with radioligand binding assay (RBA).

All chicks after hatching were divided into three groups: unilateral lid suture, lid-suture and treated with Apo subconjunctival injections and normal control. After two weeks, they were refracted, then were killed, their equator dimensions of the eyeballs were measured quickly, the retinas were dissected out and pooled into three above separate groups. [(3)H]SCH 23390 and [(3)H] Spiperone were used for the saturation tests for D(1) and D(2) receptor protein respectively in the three groups.

The numbers of both dopamine receptors in FDM increased (up-regulation). With the treatment of Apo, the numbers of both dopamine receptors decreased (down-regulation). The affinities of both receptors were of no difference.

The dopamine receptors in chick retina are under hypersensitive state in FDM, that is related to the biological level lowering of dopamine. Apo can inhibit the development of myopia, and the D(1) and D(2) receptor numbers are decreased, showing that Apo can affect dopamine receptors in various degrees. The method of this study can provide a route to screen drugs for treatment of myopia.