[Evaluation of the inhibitory effect of circulating corticosteroids on circadian stimulated and stress induced secretion of ACTH in rats].
Male rats were bilaterally adrenalectomized in order to measure the extent of inhibition exerted by endogenous corticosteroids on both basal ACTH secretion along its circadian rhythm and ether-stress induced ACTH secretion. In intact controls, plasma ACTH levels at the circadian maximum exceeded by 4 times the circadian minimum, and ACTH response 15 min after ether-stress surpassed the circadian minimum by 20 times. In adrenalectomized rats, the daily minimum was 8 times that of the controls. Nevertheless the circadian maximum was 3 times above the rhythm's minimum, while the maximal stress response (15 min) surpassed the circadian minimum by 8 times. In adrenalectomized rats supplemented with a solid source of corticosterone inducing a stable plasma corticosterone level equivalent to the controls' circadian minimum (3 micrograms/100 ml), the ACTH rhythm still fluctuated twice as high as in intact controls. The tonic feed-back inhibition exerted by endogenous corticosteroids on ACTH secretion appeared thus significantly stronger than the GABAergic inhibition to the corticotropic system which was previously studied under similar standard conditions.
D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism*; D000818:Animals; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood* / Q000494:pharmacology; D004986:Ether; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000097:blood*
D004986:Ether; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone
Evaluation de l'effet inhibiteur des corticostéroïdes circulants sur la stimulation circadienne et induite par le stress de la sécrétion de l'ACTH chez le rat.