A behavioral assessment of arcuate nucleus damage after a single injection of monosodium glutamate.

The behavioral and histological consequences of the administration of a single injection of monosodium glutamate (MSG) to neonatal mice, were examined. Profound neuronal loss was evident in the arcuate nucleus of mice administered 4 mg/g MSG on postnatal day 4. Adult MSG-treated mice were obese and hypophagic despite significantly elevated activity levels. In addition, these obese MSG-treated mice maintained their hypophagia even in the presence of a food restriction schedule which resulted in significant weight loss. MSG-treated mice were hypodipsic, but did not differ from controls in their response to adulteration of their drinking water with sodium chloride, saccharin or quinine. These studies demonstrate that a single neonatal injection of MSG is sufficient to produce dramatic behavioral alterations.