Responses of the porcine pituitary-adrenal axis to chronic intermittent stressor

Initial responses and adaptation of the porcine pituitary-adrenal axis to a chronic intermittent stressor (45-min daily restraint for 8 or 9 d) and effects of this stressor on binding to adrenocortical ACTH receptors were measured. Blood samples were obtained via indwelling jugular catheters on days 1, 5, and 9. On day 9, barrows (castrated male pigs; 40 kg) were killed and adrenal glands obtained. Binding to adrenal ACTH receptors was measured using [ 125I]Tyr 23,Phe 2,Nle 4ACTH(1–38) analog. Basal (prestressor) ACTH, cortisol, and PRL concentrations were not affected by 9 d of 45-min restraint daily (RES-9). In RES-9 barrows, integrated ACTH responses to restraint decreased 46% (P