Alpha 2-adrenoreceptor subtypes regulate ACTH and beta-endorphin secretions during stress in the rat.
The effect of different alpha 2-adrenoreceptor subtype agonists and antagonists on adrenocorticotrop hormone (ACTH) and beta-endorphin release induced by ether stress was examined. Ether inhalation-induced ACTH and beta-endorphin increase was inhibited by i.c.v. administration of 30 micrograms but not 1 and 10 micrograms clonidine (alpha 2-adrenoreceptor agonist). I.c.v. oxymetazoline (alpha 2A-adrenoreceptor agonist; 1-10-30 micrograms) or the alpha 1-agonist methoxamine (100 micrograms/rat) failed to inhibit the stress-induced rise. Pretreatment with the alpha 1/alpha 2B.C-antagonist prazosin (0.5 mg/kg, i.p.) prevented the effect of clonidine on the ether stress, while the alpha 1/alpha 2A-antagonist WB-4101 (0.5 mg/kg, i.p.) was unable to counteract the inhibitory effect of clonidine. Prazosin alone had no effect on the ether-induced plasma ACTH and beta-endorphin elevation. These results suggest that noradrenaline in the central nervous system may inhibit the stress-induced hypothalamo-pituitary-axis and pituitary beta-endorphin activation via alpha 2B.C-adrenoceptor subtypes and prazosin may antagonize its effect on these receptors.
Zelena
D
D
Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.
Kiem
D T
DT
Barna
I
I
Makara
G B
GB
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D004986:Ether / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013312:Stress, Physiological / Q000139:chemically induced / Q000503:physiopathology*; D001615:beta-Endorphin / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D011942:Receptors, Adrenergic, alpha; D004986:Ether; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; C010654:(2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane; D008729:Methoxamine; D003000:Clonidine; D011224:Prazosin