Central effect of the enkephalin analogue FK-33824 on vasopressin secretion in conscious sheep.
The role of opioids in the regulation of arginine vasopressin release from the posterior pituitary is a subject of controversy. In the present study, we examined the effects of central administration of met-enkephalin, leu-enkephalin, the enkephalin analogue FK-33824, and the opiate antagonist naloxone, and the effects of systemic administration of met-enkephalin and FK-33824 on AVP secretion in conscious normal sheep. Intracerebroventricular infusion of FK-33824 significantly increased the plasma concentration of immunoreactive AVP in a dose-dependent manner, but met-enkephalin, leu-enkephalin and naloxone failed to change plasma concentration of AVP. Intravenous infusion of met-enkephalin and FK-33824 also failed to change plasma concentration of AVP. The opiate antagonist naloxone given both centrally and systemically attenuated the increase in plasma concentration of AVP induced by FK-33824. We conclude that basal AVP release is stimulated by central administration of FK-33824.
Wang
X M
XM
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Australia.
Tresham
J J
JJ
Congiu
M
M
Scoggins
B A
BA
Coghlan
J P
JP
D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood / Q000378:metabolism*; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000008:administration & dosage*; D004744:Enkephalin, Methionine / Q000008:administration & dosage; D005260:Female; D007262:Infusions, Intravenous; D007276:Injections, Intraventricular; D009270:Naloxone / Q000008:administration & dosage; D012756:Sheep
D001127:Arginine Vasopressin; D009270:Naloxone; D004744:Enkephalin, Methionine; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin