Stimulus-Induced Corticotropin-Releasing Factor Content and Adrenocorticotropin Release Are Augmented after Unilateral Adrenalectomy, Independently of Circulating Corticosteroid Levels*

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Abstract
There is evidence for a neural link between the adrenal and hypothalamus that may mediate increased corticotropin- releasing factor and ACTH secretion within seconds after bilateral adrenalectomy. These studies on young male rats tested the possibility that functional evidence for adrenal afferent nerves might be revealed by the application of ACTH-releasing stimuli after the acute ACTH and corticosteroid responses to unilateral or sham adrenalectomy had subsided. Resting ACTH and corticosterone levels were not different in the two groups 1, 3, or 7–10 days after adrenal surgery. Despite similar initial conditions, the ACTH response to ether or to laparotomy with intestinal traction (but not to ip saline injections) was greater after unilateral adrenalectomy (P < 0.01) at times when plasma corticosterone levels were not different. Hypothalamic corticotropin- releasing factor-like activity was higher in unilaterally adrenalectomized than in sham-operated rats 2 min after exposure to ether (P < 0.05). We conclude that these results may represent a functional demonstration of decreased inhibitory neural feedback from the adrenal to the hypothalamus after unilateral adrenalectomy, and discuss the possibility that the absence of neural feedback may contribute to the well known hyperresponsiveness of bilaterally adrenalectomized rats to ACTH-releasing stimuli. (Endocrinology106: 1410, 1980)