Estradiol inhibition of catecholamine elicited eating in the famale rat

Two experiments test the hypothesis that estradiol suppresses food intake by inhibiting β dopamine hydroxylase in the anterior diencephalon where norepinephrine sensitive neurons activate feeding behavior. In the first experiment, dopamine or norepinephrine was injected intracerebrally in female rats during estrous and diestrous phases of the estrous cycle. Dopamine injections in the anterior diencephalon of rats elicited eating (p<0.05) only during diestrus when circulating estradiol is low; norepinephrine elicited eating during both diestrous (p<0.02) and estrous (p<0.001) phases of the cycle. In the second experiment the catecholamines were administered to ovariectomized rats with and without estradiol replacement. Again dopamine was effective in eliciting food intake (p<0.05) only in the absence of circulating estradiol while the increases following norepinephrine were independent of estradiol treatment.