Exogenous levodopa increases the neuro retinal dopamine of guinea pig myopic eyes in vitro.

In our previous work, it has been shown that intraperitoneal injection of L-DOPA can inhibit the development of occlusion myopia in guinea pigs, and increase levels of retinal dopamine. The aim of this study was to investigate whether exogenous L-DOPA can be converted into dopamine in cultured retina of guinea pig eyes subjected to visual deprivation, and to evaluate whether müller cells are involved in the processing of retinal dopamine induced by L-DOPA.Fifty-eight guinea pigs were randomly divided into 2 groups at the age of 4 weeks: normal control and visual deprivation. Form deprivation was induced with translucent eye shields over the right eye, and lasted for ten days. Corneal curvature, refraction and axial length were measured in all animals. In vitro, neuro-retina and müller cell were cultured, and L-DOPA was added to the culture medium at three concentrations: 1цM, 10цM and 100цM. Subsequently, dopamine content was evaluated by high-performance liquid chromatography, and apoptotic cells were identified by TUNEL staining.Ten days of occlusion caused the affected eyes to elongate and become myopic in guinea pigs. Compared with the deprivation group, 10цM L-DOPA treament significantly raised dopamine content in cultured retina and müller cells (P<0.05). However, 1цM and 100цM L-DOPA treatment caused no increase in dopamine levels (P>0.05). Apoptotic nuclei were detected in the ganglion cell layer (92.5%±8.3%) and inner nuclear layer (46.8%±9.1%) of cultured retina treated with 100 цM L-DOPA. Moreover, 100 цM L-DOPA also caused apoptosis of retinal müller cells, at a mean rate of 59.4 ±11.3%.Our results suggest that exogenous L-DOPA can cause an increase in retinal dopamine in form-deprived guinea pig eyes in vitro, and that müller cells are involved in the increase in retinal dopamine.