Abstract: OBJECTIVE: To investigate mechanism-based anti-anxiety effects of Shudihuang (Radix Rehmanniae Preparata) polysaccharides (RRPPs) through two-dimensional electrophoresis (2-DE) analysis with mass spectrometry (MS) of hippocampus proteins in rats treated with monosodium L-glutamate (MSG).METHODS: MSG (4 g/kg) or normal saline (NS) was injected subcutaneously into infant male rats on days 2, 4, 6, 8, 10 after birth. MSG-treated rats at 8 weeks old were given NS, diazepam, or RRPPs daily for seven consecutive days by intragastric administration, while NS-treated rats given the same volume of NS. Elevated plus maze (EPM) and light/ dark transition (LDT) tests were used to observe anti-anxiety effects of RRPPs at 1 h after the last administration. After EPM and LDT tests, hippocampus tissues were excised on ice rapidly from the brains of rats. Thereafter, 2-DE and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) were used for detecting differential proteins in hippocampus of rats so as to explore the potential mechanisms. RESULTS: RRPPs (200, 400 mg/kg) could significantly inhibit MSG-induced decrease of time and entries percentages in open zones in EPM test and numbers of light-dark transition in LDT test. Further analysis of 2-DE and MALDI-TOF/MS indicated that β-synuclein, protein DJ-1, peroxiredoxin-2, peroxiredoxin-6, dimethylarginine dimethylaminohydrolase 1 (DDAH-1) and iron-sulfur proteins were all found to be down-regulated significantly in MSG-treated rats, while such down-regulation was significantly inhibited after treatment with RRPPs. CONCLUSION: RRPPs showed anti-anxiety effects and potential mechanisms might be related to inhibiting MSG-induced down-regulation of β-synuclein, DJ-1, peroxiredoxin-2, peroxiredoxin-6, DDAH-1 and iron-sulfur proteins in hippocampus of rats.

Key words: Electrophoresis, gel, two-dimensional, Beta-synuclein, DJ-1 protein, Peroxiredoxins, Dimethylargininase, Iron-sulfur proteins, Anti-anxiety agents