Effect of variations in adrenocortical function on dopamine beta-hydroxylase and norepinephrine in the brain of the rat

The effect of adrenalectomy and corticosterone treatment on dopamine beta-hydroxylase (DBH) activity, catecholamine content and norepinephrine formation and metabolism were studied in the hypothalamus and other parts of the brain of male rats. Two days after adrenalectomy, there was a decrease in DBH activity in the hypothalamus and the brain stem but no change in norepinephrine or dopamine content. Conversion of intraventricularly administered tritiated dopamine to tritiated norepinephrine was slightly increased and norepinephrine was metabolized at a more rapid rate than normal. Corticosterone in a dose of 100 mg/kg increased DBH activity but decreased hypothalamic norepinephrine and copamine content. In adrenalectomized rats, smaller, more physiological doses of corticosterone did not change DBH activity or catecholamine content. The fact that norepinephrine formation and metabolism were increased at the same time that DBH activity in vitro was decreased suggests that DBH is not rate-limiting in adrenergic neurons in the hypothalamus, or that a change in the in vitro activity of the enzyme was not accompanied by a parallel change in its activity in vivo.