Effect of stress, adrenocorticotropin or corticosteroid treatment, adrenalectomy, or hypophysectomy on hypothalamic immunoreactive adrenocorticotropin concentrations.

Despite variations in plasma and/or pituitary ACTH concentrations, no changes in median eminence or medial basal hypothalamic immunoreactive ACTH-like concentrations were seen in rats studied 6 weeks posthypophysectomy, 12 h or 28 days after bilateral adrenalectomy, 6 days after implantation of corticosterone pellets (75 mg), after dexamethasone administration (300 micrograms/100 g BW, ip, twice daily for 4 days), or after chronic immobilization stress. The lack of concordant variation of brain, pituitary, and plasma ACTH concentrations further supports the suggestion of a nonpituitary, central nervous system origin of some portion of brain immunoreactive ACTH-like activity.