Electrical activity of the rat uterus during early pregnancy and abortion

Electrical activity of the rat uterus was recorded for 1 h daily on days 2--9 of pregnancy with 6 electrodes chronically implanted in the left uterine horn. In 10 untreated and 7 ergocornine treated rats, activity decreased in frequency and intensity during the first days of pregnancy. After day 3 activity was present in only about 30% of electrodes as compared to 85% on day 2. Abortion was induced by ergocornine injected on day 5. In these rats the frequency of bursts increased on days 8 and 9. During the peak of activity the majority of bursts spread in the cervical direction.