1. Abstract
Monosodium glutamate (MSG) is a popular flavor enhancer used in food industries;
however, excess MSG is neurotoxic. Oxidative stress is well documented in MSG
induced neurotoxicity. MSG was administrated to Swiss albino mice of 4 weeks at doses
of 1.5, 2.0 and 2.5 g/Kg body weight for 12 days through intraperitoneal (i.p) injection
in three different groups. At the end of the treatment period, animals were assessed for
behavioral activity and were sacrificed; brains were isolated for histopathological study
and brain phospholipid estimation. Plasma and serum were collected to perform
biochemical tests: ALT, creatinine, total protein, triglyceride (TG), total cholesterol,
plasma glucose. Hemoglobin assay was done with the whole blood. Body weight was
significantly decreased at high dose of MSG. As body weight is affected there was a
possibility that MSG might have some deleterious effect on the brain. To find out this,
animal model was placed in the Y maze test, and, the Morris water maze (MWM) test.
The data showed that MSG treated mice failed to recognize a specific arm in the Y maze
test, and, failed to recognize a hidden platform in the MWM test indicated that their
memory was somehow affected. As hippocampus (mostly CA regions) plays an
important role in the memory formation, there was a possibility that the cells of
hippocampus will be affected. As for the histopathological observation of the brain
hippocampus, cells of CA1 layers are found to be affected, while CA2, CA3, and,
dentate gyrus (DG) were unaffected (Nissl staining was performed), which suggests the
damage in neuronal and glial cells in the brain occurs due to MSG administration. In
regard to liver functions, the activities of alanine aminotransferase (ALT) was found to
be increased in the plasma, with MSG administration, meanwhile, plasma total protein
level was found to be decreased. MSG had adverse effects on kidney functions as
plasma creatinine were found to be increased. Plasma glucose level decreased non-
significantly. Hemoglobin level was also found to be decreased indicated that MSG
might have a deleterious effect on hematological parameters. The total cholesterol level
was found to be decreased. The brain phospholipid level was also found to be decreased
after MSG treatment. Basically, all lipids in the brain have a role in modifying the
structure, fluidity, and function of cellular and subcellular membranes and in myelin.
Thus, decrease in brain phospholipid indicates the deleterious effect of MSG in brain
function.
Key words: Monosodium Glutamate, Neurotoxicity, Hippocampus, Nissl staining