Effects of monosodium glutamate and gold thioglucose on dietary regulation of sympathetic nervous system activity in rodents.

Neonatal administration of monosodium glutamate (MSG) disrupts hypothalamic regulation of a number of neuroendocrine systems. Studies described in this report using techniques of norepinephrine (NE) turnover examined sympathetic nervous system (SNS) activity in heart and interscapular brown adipose tissue (IBAT) of animals given MSG as neonates. Although in every experiment overall rates of NE turnover were lower in MSG-treated mice and rats, the differences were due exclusively to diminished tissue NE content, especially in IBAT. Fractional rates of NE turnover did not differ between groups. In contrast to animals with lesions in the ventromedial hypothalamus produced by gold thioglucose (AuTG) or electric current, MSG-treated mice and rats varied SNS activity in heart and IBAT in accord with changes in nutrient intake. Thus, SNS activity, both at baseline and in response to dietary manipulation, is probably not affected by neonatal MSG administration.