An analysis of the characteristics of the electromyogram recorded from the mesometrium in the ovariectomized nonpregnant ewe and its similarities with and differences from the electromyogram obtained from the myometrium: the effect of estrogens.

Mesometrial and myometrial electromyograms have been recorded from ovariectomized nonpregnant ewes. After infusion with saline solution, the frequency of electromyographic events lasting less than 180 seconds in the myometrium was not different from the frequency of their occurrence in the mesometrium. During infusion of estradiol at 100 micrograms/24 hours, the frequency of events less than 180 seconds increased significantly in the myometrium but was unchanged in the mesometrium. Contracture activity (electromyographic events lasting more than 180 seconds) was significantly greater in the mesometrium than in the myometrium before estradiol administration. During estradiol infusion, contracture activity remained unchanged. These findings suggest that the mesometrial muscle may be a useful model to study the effects of various stimulators and inhibitors of uterine muscle function in the absence of stretch and local paracrine effects that occur in the uterus itself.