Relationship between pituitary ACTH content and hypothalamic catecholamines in the rat

Hypothalamic concentrations of epinephrine and norepinephrine were determined in rats following 6-hydroxydopamine lesions of the locus coeruleus and subcoeruleus system and following sham-operation. These concentrations were correlated with pituitary ACTH content. While the lesion procedure did not have a major effect on hypothalamic monoamine levels, we were able to demonstrate a strong negative correlation between hypothalamic epinephrine and pituitary ACTH content independent of the experimental condition. Only a weak negative correlation was observed for hypothalamic norepinephrine and pituitary ACTH. Our recent and previous data suggest a tonic and phasic inhibition of ACTH release by hypothalamic monoamines.