A temporal study of post-adrenalectomy increase in ACTH secretion in the rat: effect of various hypothalamic...

Adult male rats, intact (N) or with complete (CHD), anterior (AHD), or posterior (PHD) hypothalamic deafferentations were bilaterally adrenalectomized. At 3, 6, 12 and 20 days post-adrenalectomy they were decapitated and trunk blood was collected for ACTH determinations. In N rats, ACTH markedly elevated up to 850 pg/ml. A similar ACTH response was found in PHD rats but the values were lower by approximately 20%. In contrast, in either AHD or CHD rats, ACTH responses were markedly attenuated and reached a plateau of about 350 pg/ml. These data suggest that: (1) neural inputs entering the medio-basal hypothalamus (MBH) from both the caudal and rostral directions are important for obtaining maximal ACTH responses following adrenalectomy; (2) at least part of this ACTH response is mediated by sites inside the MBH or in the pituitary.