Stimulation of fetal hypothalamus induces uterine contractions in pregnant rats at term.

The fetal brain is thought to have a role in the onset and progression of labor. Evidence also exists for fetal oxytocin release just before and during parturition. The present study examined whether activation of the fetal brain could induce uterine myometrial contractions through oxytocin receptors in the dam. Under urethane anesthesia, electrical stimulation of the hypothalamus of fetal rats that were still connected with the dams by an intact umbilical cord induced uterine contractions in term pregnant rats. Intraperitoneal injections of synthetic oxytocin in fetuses induced uterine contractions in the dams similar to those induced by electrical stimulation of the fetal hypothalamus. Maternal intravenous injections of an oxytocin antagonist immediately attenuated uterine contractions induced by fetal oxytocin injections and electrical stimulation of the fetal hypothalamus. These findings suggest the possibility that oxytocin released from the fetal hypothalamus is involved in parturition.