Objectives: Monosodium glutamate, the salt of glutamic acid, is largely used as a flavour enhancer (E621). In this study, we determine if monosodium glutamate, after repeated oral administration, can induce any degree of anxiety. Taking into account the interdependence between glutamate and GABA neurotransmissions, we studied the possible interactions of monosodium glutamate with some representatives belonging to benzodiazepines therapeutical class, diazepam and alprazolam, used as first line therapy for the treatment of anxiety.
Methods: For determining the degree of anxiety, the specific cross-labyrinth test was used. The medium time spent in the closed-arms of the cross-labyrinth is correlated with increased anxiety and the medium time spent in the opened arms is correlated with a low degree anxiety. NMRI adult mice received 300 mg/kg monosodium glutamate for 21 days, dose representing 1/50 from mice LD50 (15000mg/kg) and twice the maximum admitted dose/ day for human.
Results: When compared to control group, the group receiving monosodium glutamate, showed a not statistically significant slight increase in the degree of anxiety. The groups receiving benzodiazepines presented a significant reduction of the degree of anxiety, proving their anxiolytic effect. The groups receiving glutamate and diazepam or alprazolam, showed a lower reduction of the degree of anxiety, than group receiving only benzodiazepines, phenomenon which proves an antagonism between glutamate and the anxiolytics used in this study.
Conclusions: The oral administration of monosodium glutamate increases slightly, not statistically significant, the degree of anxiety in mice and significantly alters the response to the benzodiazepines therapy, reducing the effect for both alprazolam and diazepam.