The Effect of GDNF on the Expression of Retinal EAAT-1 and GS of Rats after Optic Nerve Axotomy

Objective: To investigate the effect of exogenous Glial cell derived neurotrophic factor (GDNF) on the expression of retinal excitatory amino acid transporter-1 (EAAT-1) and glutamine synthetase (GS) of rats after optic nerve axotomy. Methods: Right unilateral optic nerve crush (ONA) model of Sprague-Dawley rats (56) was established, and divided into 4 groups randomly. Right eyes of each group were injected intravitreously 1 μg (test 1 group), 2 μg (test 2 group ), 3 μg ( test 3 group) GDNF, and 0.1 M phosphate buffered saline (negative control group) after ONA immediately. Injections were repeated 7 days after ONA. The left eyes of negative control group were intact, and served as normal control group. FluoroGold was injected into the superior colliculi of 2 rats out of each group to retrogradely label retinal ganglion cells in order to examine the optic nerve axotomy. The expression of GS, EAAT-1 of each group was tested with immnohistochemisty 14 and 21 days after ONA. Results: Retinal ganglion cells axotomy were confirmed by FluoroGold retrogradely labeling. The expression of EAAT-1, GS of normal control group and test 2 group was high significantly than that of negative control group at 14, 21 days after ONA. The expression of GS of test 3 group was also high significantly than that of negative control group at 14 days after ONA. The expression of EAAT-1, GS of test 1 group was lower than that of normal control group at 21 days after ONA. Conclusion: Exogenous GDNF injected intravitreously with adequate dose can enhance the expression of EAAT-1, GS after optic nerve axotomy.