Pituitary adrenocortical activity and intermale aggressiveness in isolated mice

Three experiments were conducted to clarify the role of the hormones of the pituitary adrenocortical axis in the control of intermale aggressiveness in mice. The first experiment tested the possibility that adrenalectomy decreases aggressiveness through decreasing androgen levels by treating adrenalectomized mice with testosterone propionate. None of the dosages of testosterone used in this study were effective in restoring the aggressiveness of adrenalectomized mice. The second and third experiments examined whether manipulations of pituitary adrenocortical activity affect aggressiveness because of changes in ACTH levels or because of changes in circulating glucocorticoid levels. In the second experiment, dexamethasone treatment restored the aggressiveness of adrenalectomized mice; and in the third experiment, ACTH decreased the aggressiveness of both intact mice and mice with controlled levels of corticosterone and/or testosterone. These findings suggest that ACTH levels, rather than glucocorticoid levels, are the critical parameters in the control of aggressiveness by the hormones of the pituitary adrenocortical axis and that ACTH affects aggressiveness independently of its effects on either adrenocortical or gonadal activity.