Met-enkephalin and the enkephalin analogue FK-33824 centrally inhibit adrenocorticotrophic hormone secretion in sheep.
1. The effects of central administration of met-enkephalin, leu-enkephalin, the enkephalin analogue FK-33824 and the opiate antagonist naloxone on plasma concentration of adrenocorticotrophic hormone (ACTH) were examined in conscious sheep. 2. Intracerebroventricular infusion of met-enkephalin and FK-33824 significantly decreased the basal plasma concentration of ACTH. 3. Intracerebroventricular infusion of FK-33824 inhibited the haemorrhage-induced increase in plasma concentration of ACTH. 4. Intracerebroventricular infusion of naloxone attenuated the central inhibition of plasma concentration of ACTH induced by FK-33824, but intravenous infusion of naloxone had no effect on the reduction in plasma concentration of ACTH induced by FK-33824. 5. These studies suggest that in sheep met-enkephalin may play a central inhibitory role in the control of ACTH secretion.
Wang
X M
XM
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria, Australia.
Tresham
J J
JJ
Scoggins
B A
BA
Coghlan
J P
JP
D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D005260:Female; D009270:Naloxone / Q000494:pharmacology; D012756:Sheep
D009270:Naloxone; D004744:Enkephalin, Methionine; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D000324:Adrenocorticotropic Hormone