Albino rats of Wistar strain with normal sexual cycle on the basis of their vaginal smears were used and anesthetized with Mintal (pentobarbital) injecting 5 mg/100 g intraperitoneally in acute experiments. Spontaneous electromyographic activity of the rat uterus in vivo was recorded using a concentric electrode (silver wire, 50μ diameter). One electrode was placed in the tubal side and the other electrode in the cervical side of a corpusuteri of the rat. Electromyographic recordings were made with a 2 channel inkwritingapparatus. The spontaneous electrical activity of the rat uterus in situ could be observed through the cycle. The basic electromyographic patterns of the nonpregnant ratuterus at the estrus were the train of spike and the spike burst. From proestrus to estrus, the spontaneous spike discharges increased in amplitude and in frequency and became of a set of their discharges. In some cases the spontaneous spike discharges were observed sporadically at the diestrus of the cycle and the castrated condition.
