title: Inhibition of oxytocin-induced uterine contractions by an oxytocin antagonist in the pregnant baboon.
abstract: Uterine contractions were induced with oxytocin in anesthetized pregnant baboons (Papio anubis) at three stages of pregnancy (days 140, 156, and 169; normal gestation length, 184 days). After the contractile activity was greater than two to three contractions every 10 minutes, beta-mercapto-beta, beta-cyclopentamethylenepropionic acid1-[D-Trp2,Phe3,Ile4,Arg8]-oxytocin, a novel oxytocin antagonist produced in our laboratories, was given simultaneously with the oxytocin for 90 minutes. Contractile force (frequency x mean amplitude) was determined for 30 minutes before and for three 30-minute intervals after the oxytocin antagonist was administered. Animals at 140 days' gestation showed a significant (p less than 0.05) decrease in contractile force in the first 30-minute interval after oxytocin antagonist infusion was initiated, whereas those at days 156 and 169 showed decreases (p less than 0.05) at the second 30-minute interval. In addition, in late gestation a higher dose of oxytocin antagonist per unit of oxytocin was required to prevent uterine contractions. In conclusion, these results suggest (1) that an oxytocin antagonist can inhibit oxytocin-induced uterine contractions in the pregnant baboon and (2) that the interval from oxytocin antagonist administration to significant inhibition of uterine contractions appears to increase with advancing gestational age.
authors.affiliation: Department of Obstetrics and Gynecology, University of Illinois, College of Medicine, Chicago, IL 60612.
authors.forename: L
authors.initials: L
authors.lastname: Wilson
authors.forename: M T
authors.initials: MT
authors.lastname: Parsons
authors.forename: G
authors.initials: G
authors.lastname: Flouret
mesh_terms: D000818:Animals; D005260:Female; D005323:Fetal Monitoring; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000494:pharmacology; D010215:Papio; D011247:Pregnancy; D015145:Tocolysis; D014590:Uterine Contraction / Q000187:drug effects*; D014667:Vasopressins
chemical_list: D014667:Vasopressins; C066604:oxytocin, beta-mercapto-beta,beta-cyclopentamethylenepropionic acid-Trp(2)-Phe(3)-Ile(4)-Arg(8)-; D010121:Oxytocin