title: Brain angiotensin-II partially mediates the effects of relaxin on vasopressin and oxytocin release in anesthetized rats.
abstract: Experiments were conducted in anesthetized rats to assess the contribution of the brain angiotensin-II system in the relaxin-induced secretion of vasopressin and oxytocin. Intravenous injection of porcine relaxin (5 micrograms) caused a significant (P < 0.05, by analysis of variance) increase in plasma concentrations of both hormones. Peak concentrations of both vasopressin (75.2 +/- 2.9 pmol/liter) and oxytocin (38.4 +/- 1.2 pmol/liter) were observed 1-2.5 min after relaxin injection. Thereafter, concentrations fell significantly (P < 0.05) but remained elevated for a further 25 minutes. Continuous infusion of a specific angiotensin-II receptor antagonist into the lateral cerebral ventricle did not affect baseline levels of either vasopressin or oxytocin, but did significantly reduce (P < 0.05) the relaxin-induced release of both peptides. A significant (P < 0.05) short term increase in both plasma vasopressin and oxytocin occurred 1 min after injection of 5 micrograms relaxin, iv, in angiotensin-II-antagonized rats, but the concentrations of both neuropeptides were significantly (P < 0.05) lower than those observed in the angiotensin-intact relaxin-treated controls. These data suggest that relaxin may act through the central angiotensin-II system to induce the release of vasopressin and oxytocin.
authors.affiliation: Department of Biomedical Sciences, University of Guelph, Ontario, Canada.
authors.forename: B J
authors.initials: BJ
authors.lastname: Geddes
authors.forename: L J
authors.initials: LJ
authors.lastname: Parry
authors.forename: A J
authors.initials: AJ
authors.lastname: Summerlee
mesh_terms: D000758:Anesthesia; D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000502:physiology*; D005260:Female; D010121:Oxytocin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012065:Relaxin / Q000008:administration & dosage / Q000494:pharmacology*; D014667:Vasopressins / Q000378:metabolism*
chemical_list: D014667:Vasopressins; D000804:Angiotensin II; D010121:Oxytocin; D012065:Relaxin