Plasma catecholamines do not participate in pituitary-adrenal activation by immobilization stress in rats with transection of nerve fibers to the median eminence.

Abstract

The effect of immobilization stress was studied in rats in which the CRF and arginine vasopressin-containing innervation of the median eminence was destroyed by an anterolateral cut (ALC) around the medial basal hypothalamus. One week after surgery, the rats with ALC were subjected to immobilization and they showed a normal rise in plasma corticosterone, a smaller than normal rise of plasma ACTH, and an increased response of plasma epinephrine and norepinephrine. When in rats with an ALC the response of plasma catecholamines was prevented by guanethidine pretreatment and adrenal enucleation the small rise in plasma ACTH was unchanged during immobilization. In addition, the plasma corticosterone and ACTH rises during immobilization in the rats with ALC were not influenced by prior treatment with phentolamine (2.5 mg/kg ip) or propranolol (2.5 mg/kg ip). These findings suggest that the large rises in plasma epinephrine and norepinephrine levels during immobilization do not contribute to changes in plasma ACTH or corticosterone levels when hypothalamic regulation via CRF and/or arginine vasopressin is interrupted by ALC.