Electrical and mechanical activity of the cervix in the ewe during pregnancy and parturition

Abstract

Myoelectrical and mechanical activities of the uterine cervix and horns of ewes fitted with electrodes and strain gauges were measured from the 30th day before until the 3rd day after parturition. During pregnancy, cervical electromyograms presented regular episodes of strong activity of a mean duration of 7 min, termed regular spiking activity, occurring at about 50-min intervals. Between two episodes, isolated or low frequency spikes occurred randomly and constituted the irregular spiking activity. The alternation of irregular and regular spiking activities was called the myoelectrical complex of the cervix. Clear relationships were noticed between electrical and mechanical events. On the pregnant uterine horn (singleton pregnancy) or on both horns (twin pregnancy), a myoelectrical complex pattern similar to that of the cervix was recorded. Regular spiking activity on the cervix and pregnant horn(s) occurred mainly simultaneously.No significant evolution of the myoelectrical complex pattern was noted throughout the last month of pregnancy until 2\p=n-\3 days before parturition. The activity pattern was then modified according to three characteristic phases: (1) a phase of relative inhibition of the cervix and pregnant horn(s) 48 h before lambing and lasting about 17 h; (2) a phase of increasing activity occurring thereafter over the whole genital tract with an average duration of 31 h; and (3) a phase of continuous activity of the cervix and uterus for 0\ m=. \ 4\ p=n-\ 3\ m=. \ 8h which accomplished the expulsion of the lamb.It is concluded that during the last month of pregnancy the cervix is active and that its activity arises from a basic ultradian rhythm involving the entire genital tract. Furthermore, although our results do not offer an explanation for the preparturient increase of cervical compliance described by others, they definitely excluded cervical muscular inhibition during the last 24 h of pregnancy and at the time of cervical dilatation.

Cervical diameter in relation to uterine and cervical EMG activity in early postpartum dairy cows with retained placentas after PGF2alpha induced calving

“…These bursts are usually associated with contractions, as reflected by changes in intra uterine pressure [14,31]. The observation that the pattern of EMG activity of the cervical muscular layer appeared to be less well organized, corresponds with our findings in the same cows before fetal expulsion [24] as well as with findings in postpartum sheep [22]. Secondly, the decrease of the RMS values and maximal EMG amplitudes in the cervical muscular layer was less substantial than in the uterus and showed much variation between cows.…”

“…It has been shown before that the cervix displays its own contractility pattern during parturition and that its response to prostaglandin E and oxytocin differs from that of the uterus [22,24,37]. Our study shows that such differences in contractility also exist after parturition and further emphasizes that the cervix has to be regarded as an organ with an own function and acting partly independent of the uterus.…”

“…The cervix shows considerable amounts of electromyographic (EMG) activity immediately after parturition which decreases to low levels between 48 and 72 h, as has been shown in sheep [22]. It could be expected that these postpartum contractions of the cervix itself influence cervical diameter which could either be a decrease or an increase of the cervical diameter, as both phenomena have been described during parturition [23,24].…”

Evaluation of the Effects of Sennosides on Uterine Motility in the Pregnant Ewe

“…The choice of the ewe as animal model could appear somewhat unex pected due to huge species differences in gas trointestinal physiology between sheep as a ruminant and the human. Nevertheless, the ovine pregnant uterus presents a characteris tic pattern of contractility throughout preg nancy which is well known [19,20] so that any disturbances induced by drugs can be easily detected. Therefore, the effects of sen nosides on the contractility of the uterus and cervix of the ewe were investigated using an electromyographic technique in vivo to eval uate the risk of inducing abortion with laxa tive doses of sennosides.…”

Pattern of electrical activity of the ovine uterus and cervix from mating to parturition

“…Mating took place during the 3rd or 4th oestrous period after surgery, and was performed 2-4 times during the day of oestrus. Integrated records were scored for periods of 24 h. Motility events were described using the terminology (regular and irregular activity) qualified in a previous paper (Toutain et al, 1983). Charts for the pregnancy period started on Day 5 (Day 0 = day of mating) and were taken until 2 days before parturition.…”