Lack of Adaptation of Acth Secretion to Sequential Ether, Tourniquet, or Leg-Break Stress

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Abstract
Adaptation to a repeated stress in male rats was studied by measuring plasma ACTH by radioimmunoassay 2.5 min or plasma corticosterone by acid fluorescence 20 min alter initiation of the stress. No adaptation was seen in the secretion of ACTH in response to ether, tourniquet, or leg-break stresses repeated at 90 min intervals 1–3 times. A marked rise in plasma ACTH concentration was produced within 2.5 min after application of each stress. Plasma ACTH always returned to basal levels by 90 rain after application of stress. Ether stress repeated at 24-hr intervals for 3 days did not produce any decrease in either the plasna ACTH or corticosterone response by the third day. These data indicate that no adaptation in ACTH secretion in response to repeated stress occurs under the conditions of our experiments.