Effects of corticosterone on the secretion of corticotrophin-releasing factor, arginine vasopressin and oxytocin into hypophysial portal blood in long-term hypophysectomized rats.
To investigate the feedback effects of corticosterone on the secretion of corticotrophin-releasing factor-41 (CRF-41), oxytocin and arginine vasopressin (AVP), hypophysial portal vessel blood was collected from control (intact) and long-term (6-8 weeks) hypophysectomized rats. In preliminary experiments in rats anaesthetized with urethane, long-term hypophysectomy resulted in a significant increase in the secretion of oxytocin and AVP; the hypothalamic contents of oxytocin and AVP were also increased in comparison with pituitary-intact rats. In long-term hypophysectomized rats anaesthetized with sodium pentobarbitone, but not with urethane, the output of CRF-41 into portal blood was increased twofold in comparison with that in control rats. In long-term hypophysectomized rats anaesthetized with pentobarbitone, the i.v. infusion of corticosterone (7.2 nmol/min) for a 2 h period of portal blood collection did not alter the secretion of CRF-41, oxytocin or AVP into portal blood; however, the secretion of CRF-41 and, to a lesser extent, AVP was significantly reduced in hypophysectomized rats by continuous corticosterone replacement, by a pellet of corticosterone implanted s.c. for 5 days before portal blood collection. These results confirm that the secretion of CRF-41 is differently affected by the anaesthetics urethane and pentobarbitone, and in long-term hypophysectomized rats show (i) that there were no apparent feedback effects of corticosterone infusion over a 2 h period on the secretion of any of the peptides studied, (ii) that late delayed feedback effects of continuous administration of corticosterone are mediated by a reduction in CRF-41 and AVP output, and (iii) that corticosterone has no effects on oxytocin secretion into portal blood.
Sheward
W J
WJ
MRC Brain Metabolism Unit, University Department of Pharmacology, Edinburgh.
Fink
G
G
D000768:Anesthesia, General; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D003345:Corticosterone / Q000494:pharmacology*; D003346:Corticotropin-Releasing Hormone / Q000097:blood; D005246:Feedback; D005260:Female; D007016:Hypophysectomy; D007031:Hypothalamus / Q000378:metabolism*; D009479:Neuropeptides / Q000097:blood*; D010121:Oxytocin / Q000097:blood; D010424:Pentobarbital; D010902:Pituitary Gland / Q000098:blood supply*; D011168:Portal System / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014520:Urethane
D009479:Neuropeptides; D001127:Arginine Vasopressin; D014520:Urethane; D010121:Oxytocin; D003346:Corticotropin-Releasing Hormone; D010424:Pentobarbital; D003345:Corticosterone