Three experiments were conducted to determine whether the pituitary-adrenocortical and pituitary-gonadal hormones are involved in the mediation of the effects of defeat on agonistic responding in mice. In Experiment 1, preventing changes in the levels of both the pituitary-adrenocortical and pituitary-gonadal hormones delayed the decrease in aggressiveness and increase in submissiveness that normally accompany defeat and prevented the decrease in aggressiveness that normally persists following this experience. In Experiment 2, preventing changes in androgen levels alone had no effect on the agonistic response patterns of defeated mice. In Experiment 3, preventing changes in corticosterone levels alone delayed the increase in submissiveness that normally accompanies defeat but did not affect the pattern of aggressive responding. These findings suggest that the pituitary-adrenocortical responses to defeat facilitate the effects of this experience on agonistic responding. It is suggested that ACTH is the primary hormone in the mediation of the effects of defeat on aggressive responding, whereas corticosterone is the primary hormone in the mediation of the effects of defeat on submissive responding.
- Agonistic behavior