Alpha 2-adrenoceptor blockade, pituitary-adrenal hormones, and agonistic interactions in XXXX .

@entity3160 @entity35647 @entity146 @entity2819 @entity9006 @entity2922 @entity35 @entity3352 @entity2661
The effects of adrenergic activation on @entity146 and the @entity146 induced endocrine changes were tested in @entity35 . Alpha 2 adrenoceptor blockers were used for enhancing activation of the adrenergic system, and changes in @entity146 were tested in resident-intruder contests. Three experiments were conducted. In experiment 1, saline injected @entity35 responded to the presence of an opponent by @entity146 and the increase in plasma ACTH and @entity2819 . Intraperitoneal administration of 1 mg/kg @entity35647 (an alpha 2 adrenoceptor antagonist) produced a several fold increase in clinch fighting and mutual upright scores, and also further enhanced the plasma ACTH and @entity2819 response. In experiment 2, the effect of three doses (0.5, 1 and 2 mg/kg) of three different alpha 2 adrenoceptor blockers @entity35647 , @entity9006 and @entity3160 were tested. All the substances increased @entity146 at 0.5 and 1 mg/kg; at 2 mg/kg the effect of @entity9006 and @entity3160 disappeared, while with @entity35647 an additional increase was obtained. In @entity3160 treated animals the enhancement of @entity146 was reduced already at 1 mg/kg. In experiment 3, @entity3352 , a potent inhibitor of the @entity2922 -induced ACTH release completely abolished the effects of the alpha 2 adrenoceptor antagonist @entity35647 : the intensity of agonistic interactions, as well as ACTH and @entity2819 plasma concentrations, returned to control levels. The possible role of @entity2661 and the stress hormones in the activation of @entity146 is discussed.
