Glutamate and depression: Reflecting a deepening knowledge of the gut and brain effects of a ubiquitous molecule

Table 1 Dietary glutamate and depression

Subject	Outcome	Ref.
Human	In non-obese participants, diets high in levels of glutamic acid were associated with greater depression symptomatology	Kumar et al[43]
Adult mice	While chronic immobilization stress decreased sodium-coupled neutral amino acid transporter (SNAT)-1 and 2 in neurons and glutamate transporter (GLT)1, SNAT3, and SNAT5 in astrocytes in the medial prefrontal cortex, glutamine—supplemented diet ameliorated these decrements	Baek et al[44]
Neonatal rats	Subcutaneous injection of monosodium glutamate (MSG) increased the immobility time in the forced swim test and the freezing reaction in the contextual fear conditioning. MSG also increased serotonin uptake in the cerebral cortices and caused deregulation of the hypothalamic-pituitary-adrenal axis	Quines et al[35]
Mice	Anxiolytic and memory-enhancing effects at low doses of MSG; however, at higher doses, anxiety and memory retardation were observed	Onaolapo et al[45]
Mice	Higher doses of dietary glutamate resulted in an increase in plasma glutamate and glutamine but no difference in total brain glutamate or glutamine levels	Onaolapo et al[21,45,46]
Mice	Anxiolytic response in females, and anxiogenic response in males following dietary MSG. A decrease in behavioural despair was observed in both sexes (females more than males)	Onaolapo et al[46,47]
Mice	Anxiogenic effect was observed following subchronic oral administration of MSG	Onaolapo et al[49]