Hypothalamic norepinephrine synthesis rate in overfed, underfed and fasted mice.

Abstract

Hypothalamic norepinephrine (NE) synthesis rate during acute (1-day and 3-day) and chronic (11-day) overfeeding (14 kcal/day) and underfeeding (7 kcal/day) and 24 hr food deprivation was determined in four-week-old female mice. Mice were fed ad lib quantity or 51% of ad lib in a meal-feeding paradigm, a 60% fat diet providing constant protein intake across groups. NE synthesis rate, during the thermic effect of a meal, was calculated from the rate of NE accumulation after monoamine oxidase inhibition by pargyline and clorgyline. Acute and chronic underfeeding versus overfeeding had no effect on NE synthesis rate in the hypothalamus or in the rest of brain, or chronically in hypothalamic nuclei. In mice deprived of food for 24 hr, NE synthesis rate in the paraventricular nucleus only was five-fold higher than in fed mice. Thus, NE synthesis rate within the hypothalamus appears to be more related to short-term food intake regulation than to the thermic effect of eating or body fat content.