Catecholamine levels and their distribution in the uterus during pregnancy and labor

Catecholaminergic fiber distribution and noradrenaline levels were studied in various sections of the myometrium of a pregnant uterus. Female myometrium preparations obtained during surgery were studied by histochemical and radioenzymic methods. The findings evidence that catecholaminergic innervation of the myometrium is essentially reduced by the end of normal pregnancy and is detectable only in the lower segment of the uterus; in labor this phenomenon is virtually undetectable. Myometrial noradrenaline++ content is reduced by 90% by the end of pregnancy and in labor, the mediator level in the lower segment of the uterus being 2.4 times higher than in the body of the uterus.