Role of fetal oxytocin in parturition in the rat.

The oxytocin (OT) content of pituitary glands from neonatal rats was reduced by parturition, indicating possible release from fetal glands during labor. The content of fetal glands fell from 2.5 ng/gland in utero to 1 ng/gland immediately after birth. Rabbit serum antibodies against OT were administered to pregnant or fetal rats preceding parturition or to lactating rats on Day 10 of lactation. Antibody administration to lactating rats resulted in a decrease in weight gain of suckling pups, indicating that OT was bound by antibody. Administration of OT antibody to pregnant rats had no effect on the duration of gestation while injection into fetal pups resulted in an 18 h increase in the mean duration of gestation compared to sham-injected controls. These studies indicate that fetal OT might have a role in initiating parturition in the rat.