Ameliorative Effect of L-arginine on Monosodium Glutamate Induced Cognitive Hypofunctions in Male Albino Rats

The present study aimed to investigate the ameliorative effect of L-arginine (L-A) on cognitive hypofunctions induced by monosodium glutamate (MSG). Thirty-six male albino Wistar rats 10 weeks old (180 to 200g) were divided into 4 groups: Group I: received distilled water, group II received L-arginine (L-A) 500 mg/kg, group III received 2 mg/kg monosodium glutamate (MSG), group IV received L-arginine 500 mg/kg and 2 mg/kg monosodium glutamate by oral gavage for 10 days. Cognitive performance was assessed using novel object recognition (NOR) and Y-maze tests. The relative brain weight of experimental rats was recorded. The malondialdehyde (MDA) level in the brain homogenate as oxidative stress biomarkers, antioxidants glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT) activities, and dopamine (DA) levels were estimated. Histopathology and immunohistochemistry to serotonin (S-2A) receptors and caspase-3 were performed. Results revealed that MSG can cause a decline in cognitive functions as evidenced by NOR and y-maze tests. Besides, it has a neurotoxic effect as evidenced by increasing MDA level and GPx activity, decreasing SOD and CAT activities, reduced DA level, histopathological alteration in the brain, decreased S-2A receptors, and increased apoptosis as demonstrated by promoted caspase-3. Treatment with L-A 500 mg/Kg BW ameliorated the neurophysiological effects of MSG through improving memory, decreasing MDA level, GPx activity, increasing SOD and CAT activities, increasing DA level, improving histoarchitecture of the brain, improving S-2A receptors and decreasing apoptosis ameliorating caspase-3 protein in the brain.