Suppression of pulsatile release of oxytocin during early pregnancy in the goat

Concentrations of oxytocin were measured in the peripheral plasma of four goats during both luteolysis in the oestrous cycle and the early stages of pregnancy. The two profiles were similar, each showing a decrease from day 12 onwards; during luteolysis, however, in the non-pregnant goats this decline was characterised by frequent pulses of oxytocin in excess of 40 pg/ml; these were absent during the corresonding period of pregnancy. It is suggested that the embryo may prevent luteal regression in pregnancy by suppressing pulsatile release of oxytocin, which may be responsible for the release of prostaglandin F_2α from the uterus.