Postpartum increases in brain oxytocin binding.

The binding of 3H-oxytocin in the forebrains of pregnant and postpartum rats was measured using an in vitro autoradiographic method. Binding increased selectively in the bed nucleus of the stria terminalis early in the postpartum period. This effect may be due to the physiologic changes in sex steroids late in pregnancy as the combination of ovariectomy and estrogen administration induced a similar increase in binding.