Evidence for Central Adrenergic Neural Inhibition of ACTH Secretion in the Rat1

The methyl ester of α-methyl-ptyrosine (α-MT), 250 mg/kg ip, increased plasma corticosterone 9 hr later in most rats studied. The increase in plasma corticosterone was correlated with the depletion of hypothalamic contents of norepinephrine and dopamine. L-dihydroxyphenylalanine (L-dopa), 100 mg/kg ip, but not L-norepinephrine, 0.5 mg/kg ip, administered simultaneously with α-MT decreased the effect of α-MT on plasma corticosterone. A significant negative correlation was found between plasma corticosterone and hypothalamic contents of norepinephrine and dopamine after administration of α-MT and L-dopa. The administration into the third ventricle of the brain of a systemically ineffective dose of α-MT increased plasma corticosterone nine hr later. These data support our hypothesis of central adrenergic neural inhibition of ACTH secretion in rats. (Endocrinology89: 1464, 1971)