Uterine electromyographic activity in the pregnant rhesus monkey showed two types of episodic electrical events, defined on the basis of duration of the episodes. One of these (designated type I in this report) was characterized by frequent bursts of electrical activity that lasted from 0.5 to 1.2 minutes (mean duration, 0.64 ± 0.007 [SE] minutes) and occurred at frequencies of 10 to 45 per hour. The other type of electromyographic activity observed (type II) consisted of fragmented series of discharges that lasted 2 to 15 minutes (mean duration, 5.45 ± 0.12 [SE] minutes) and occurred at frequencies of 0 to 6 per hour. The frequency of type I electromyographic events showed a circadian pattern of low amplitude with a maximum at night in animals with minimal uterine manipulation (electrodes only). This daily pattern was amplified during the 8 to 10 days that preceded delivery. Hysterotomy and fetal catheterization induced a circadian increase in the frequency of type I electromyographic events akin to that observed during the predelivery period. Fetal death abolished the high-amplitude circadian variation of type I electromyographic events both postoperatively and in the predelivery period. These data indicate that the fetus plays a role in the regulation of uterine type I electromyographic activity in the rhesus monkey.
ASJC Scopus subject areas
- Obstetrics and Gynecology