Reduced forebrain norepinephrine in rhesus monkeys made obese by hypothalamic lesions

Young adult male rhesus monkeys received bilateral lesions in the anteromedial lateral hypothalamus. During the year of observation following surgery the animals were hyperphagic and became markedly obese. The mean increase in body weight averaged 66% more for the experimental animals than for the controls. Analyses of catecholamine concentrations in 12 brain regions at the time of sacrifice revealed consistently lower concentrations of norepinephrine (averaging 51% of control) in the frontal cortex of the obese animals as well as a more variable decrease in norepinephrine in the caudate and striatum. There was no consistent effect of the lesions on dopamine in any of the regions studied. There was no obvious relationship between regional catecholamine levels and weight gain within the experimental group.