Effect of oral monosodium glutamate on glutamic acid levels in the nucleus arcuatus of the hypothalamus and on serum osmolality of adult and infant mice.

Monosodium glutamate (MSG) given by gavage to 7-day-old mice at 2 g/kg body weight (b.wt.) as a 20% solution w/v resulted in a 27% increase in the glutamic acid (GA) content in the nucleus arcuatus of the hypothalamus (NAH). When MSG was administered by gavage to adult mice at 4 g/kg b.wt. as a 20% solution w/v, GA levels in NAH remained unchanged. Serum osmolality, measured after oral MSG, was elevated in infant mice but was unaffected in adults.