Infusion with an oxytocin receptor antagonist delays parturition in a marsupial

Abstract

The oxytocin receptor antagonist [1-deamino-2-D-Tyr-(OEt)-4-Thr-8-Om]-oxytocin (Atosiban) is a specific antagonist of both mesotocin- and oxytocin-induced myometrial contractions in late pregnant tammars in vitro. Continuous intravenous infusion of Atosiban (1 mg kg-1 day-1) for 3 or 7 days from day 24 of the 26.5 day gestation significantly delayed births. In both the 3 day and 7 day infusion groups, all 15 control animals were pregnant and gave birth within the normal time (day 26.75 ± 0.20, mean ± SEM), during the infusion of saline. The neonates weighed 387 ± 8 mg. Deliveries were observed in 15 Atosiban-treated animals significantly (P < 0.05) later than in the controls (day 27.85 ± 0.1..