CONTINUOUS OBSERVATIONS OF SPONTANEOUS ELECTRICAL ACTIVITY OF THE PREGNANT UTERUS OF RAT IN VIVO

The spontaneous and oxytocin induced electrical activity of the pregnant uterus of rat has been studied in vivo by recording electromygorams at various stages during pregnancy. The electrical activity has been compared at different uterine portions in the pregnant uterus of rat; at the myometrium of the corpus, the cervix, the edge of the placental area, and the placental area. Also, one or two electrodes (silver wire, 50μ in diameter) were introduced into the myometrial coat at the different uterine poitions for the recording as described in the previous report. The experiments were performed on the 12th, 13th, 14th, 18th and 21st days of pregnancy. The electrical activity of the pregnant rat uterus consisted of repetitive spike discharges at the different uterine portions through various stages of pregnancy. In vivo, myometrium of the placental area showed a little spontaneous activity before term, but there was no difference between the myometrium of the edge of the placental area and of the other portions (the corpus and the cervix). No distinction between the electrical excitability of placental and nonplacental myometrium was observed at term. After the above control records were taken, oxytocin was injected in a dose of 2 or 3 i.u. intraumuscularly and the response in increase of spike discharges at the different uterine portions were clearly detected.