The effects of methylprednisolone on the expression of retinal EAAT-1 and GS of rats after optic nerve axotomy

Abstract

Objective To investigate the effects of methylprednisolone (MP) on the expression of retinal excitatory amino acid transporter-1 (EAAT-1) and glutamine synthetase (GS) of rats after optic nerve axotomy(ONA). Methods Fifty-six rats ONA models were established, and divided into group 1, group 2, group 3, and group 4 randomly with 14 rats in each group. The left eyes of group 4 were intact, and served as normal control group. Group 1, group 2, and group 4 received a dose of 10mg/kg/d, 20mg/kg/d of MP, and equal volume of normal saline respectively for 5 days while group 3 received NASCIS-II protocol dose of MP after ONA. The optic nerve condition of each group was observed with retrograde tracing of fluorogold at 7 days postoperation. The expressions of EAAT-1, GS of each group at 14 and 21 days after ONA were detected and analyzed with immnohistochemisty. Results The expression of EAAT-1 of each group was lower significantly than that of normal control group and there were no significant difference among the group 1, group 2, or group 3 at 14 days or 21 days after ONA. The expression of GS of group 4 was lower significantly than that of group 1 and normal control group at 14 days and 21 days after ONA, lower than that of group 3 at 14 days after ONA, and lower than that of group 2 at 21 days after ONA. Conclusion ONA can reduce the expression of retinal EAAT-1, GS of rats. MP can increase the expression of retinal GS rather than EAAT-1 after ONA. Key words: Optic nerve axotomy; Methylprednisolone; Excitatory amino acid transporter-1; Glutamine synthetase; Rat