The aim of this study was to investigate the effect of intraperitoneal injection of L-DOPA on refractive state and retinal dopamine in the chick form-deprived eyes and whether exogenously L-DOPA can be converted into dopamine in cultured retina. Form deprivation was induced by lid-suture in the right eyes. L-DOPA was injected intraperitoneally into the chicks once a day. All avian eyes were refracted with a streak retinoscope and its corneal radius of curvature was measured with a keratometer. Subsequently, the axial length was measured by caliper, and retinal dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC)content was evaluated by the high-performance liquid chromatography. Neural retinas in the deprived eyes were cultured in vitro, and L-DOPA was added to the culture medium at three concentrations: 1цM, 10цM and 100цM. Apoptotic cells were detected by TUNEL staining in the cultured retinas.Fourteen days of lid-suture caused the form-deprived eyes to elongate and become myopic, and retinal dopamine and DOPAC content to decrease, but the corneal radius of curvature was not affected. Repeated intraperitoneal injection of L-DOPA could inhibit the myopic shift, and raise retinal dopamine and DOPAC content in the sutured eyes. Exogenous L-DOPA (1 цM and 10 цM) significantly raised the retinal dopamine and DOPAC content, and the elevated levels in 10цM L-DOPA was higher than in 1цM L-DOPA. 100 цM L-DOPA caused no statistically significant effect on retinal dopamine and DOPAC content. However, apoptotic nuclei were detected in the retinal ganglion cell layer (92.5%±8.3%) and inner nuclear layer (46.8%±9.1%) in the 100 цM L-DOPA treatment.Systemic L-DOPA was able to partially suppress the development of form deprivation myopia, which may be associated with the compensation of retinal dopamine in chicks. |