The effect of different doses of sodium metabisulfite on learning: The role of glutamate

Objective: In our study, we investigated the effects of different dietary sodium metabisulfite doses on learning and memory processes assosiated with glutamate cycling. Method: 90 male Wistar rats were divided into three groups: control [(C)], treated with 100 mg/kg/day sodium metabisulfite [S(100)] and treated with 260 mg/kg/day sodium metabisulfite [S(260)]. Radial arm maze and open field tests were performed in order to evaluate learning and memory. Glutamate and glutamine levels were determined in the dialysate collected by microdialysis. Additionally, vesicular glutamate transporter-1 (VGLUT1), excitatory amino acid transporter-1, 2 and 3 (EAAT1, EAAT2 and EAAT3) levels were measured by reverse transcription polymerase chain reaction (RT-PCR) method in hippocampus. Results: The rats in the sulfite-treated group did not reach the criteria of 80% correct choice. The sulfite groups showed more reference and working memory errors in radial arm maze task. No significant difference was observed among open field results of groups. The levels of glutamate and glutamine in hippocampus were decreased in S(100) and S(260) groups compared with the C group. While no significant difference was found among groups' mRNA levels of VGLUT1 and EAAT2, sulfite treatment caused a dose-dependent decrease in EAAT1 and EAAT3 mRNA levels. Conclusion: Our study showed that different doses of dietary sulfite impaired learning and memory. These results implied that negative effects of sulfite in learning and memory might be mediated with glutamate cycle. Key words: Sulfite, Learning and Memory, Glutamate, Glutamine