Oxytocin-induced uterine contractions in cynomolgus monkeys. Individual infusion of 5–90 mU OT kg-1 h-1 induced stable uterine contractions of about 15–40 mmHg . No short- or long-term desensitisation of OT-induced contractions was observed. On the background of these stable OT-induced contractions, different tocolytics have been evaluated in terms of their PK/PD characteristics. Here two monkeys were infused in parallel for about 11 hours during the night. The switch-off the lights in the evening (06:00 PM) and switch-on the lights (06:00 AM) is labelled by respective symbols.