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

Garcia‐Villar, R.; Toutain, P. L.; Ruckebusch, Y.

doi:10.1530/jrf.0.0720143

Cited by 32 publications

(20 citation statements)

References 22 publications

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“…Earlier contraction studies seemed to show a fundus or corneal dominance (2,12,27). In contrast to the relative ease of determining contraction propagation, the electrical pattern seemed much more variable and therefore much more difficult to determine (13,15,28,31).…”

Section: Discussionmentioning

confidence: 99%

Patterns of electrical propagation in the intact pregnant guinea pig uterus

Lammers¹,

Mirghani²,

Stephen³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Previous studies have reported on propagation of individual spikes in isolated segments of the pregnant uterus, but there is no information on patterns of spike propagation in the intact organ. There is also no information on propagation of myometrial burst. The aim of this study was to record, at high resolution, patterns of propagation of electrical activities in the pregnant uterus. Sixteen timed-pregnant guinea pigs were euthanized at term, and their uteruses isolated. Fetuses were removed and replaced by an equal amount of Tyrode. A 240-electrode array was positioned at various locations along the organ, all signals were recorded simultaneously, and the electrical propagations were reconstructed. In the intact pregnant uterus at term, spikes propagated with high velocity in longitudinal (6.8 Ϯ 2.4 cm/s) and slower velocity in circular direction (2.8 Ϯ 1.0 cm/s; P Ͻ 0.01). Direction of propagation and frequency of activity were highly variable but showed similar patterns at the ovary or cervical end and along the anterior, posterior, and antimesometrial borders. Along mesometrium, spike propagation was sparse and fractionated. Migration of burst (0.6 Ϯ 0.4 cm/s) was significantly much slower than that of individual spikes (P Ͻ 0.001). Initial burst activity was located at variable locations along the ovarial end of the antimesometrial border, while the latest excitation occurred at the cervical end (1.2 Ϯ 0.9 min). In conclusion, high resolution electrical mapping of the intact pregnant uterus reveals fundamental properties in spatial and temporal patterns of spike and burst propagation that determine the contraction of the organ. spikes; myometrial burst migration ELECTRICAL ACTIVITY in the pregnant myometrium is characterized by phasic bursts of action potentials (spikes), which could be based on cyclic changes in transmembrane potential (24). Cyclic changes in potential resemble in some respects slow waves in the intestines and presumably propagate through the myometrium, similar to the propagation of the intestinal slow waves. In both cases, the depolarization induced by the (slow) waves initiate the opening of L-calcium channels leading to the occurrence of spikes. In the intestines, it is possible to record both slow waves and spikes with extracellular electrodes, and this made it possible to reconstruct the pattern of propagation of both signals and to study the complex interaction between these two electrical waveforms (22).In the myometrium, the basic electrical wave is too slow or its magnitude too small to be recorded extracellularly (9). The spikes, however, are visible in extracellular recordings and this led to several studies on their behavior. Miller et al. (25) analyzed spike propagation in pregnant uterine segments that were 3 ϫ 1 cm in size and showed that velocity in the longitudinal direction was much faster than in the circumferential direction. Lammers et al. (20) found similar results in equally small segments (8 ϫ 2 cm). Most of these studies were performed on isolated segments of...

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Section: Discussionmentioning

confidence: 99%

Patterns of electrical propagation in the intact pregnant guinea pig uterus

Lammers¹,

Mirghani²,

Stephen³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In addition, the peak of OTR and oestradiol receptor expression in the placentome capsule coincided with the sudden onset of regular muscular contractility in the pregnant horn of the uterus from days 49 to 66. No uterine activity was detectable before day 41 and only steady uterine activity was detected after day 66 until parturition (Garcia-Villar et al 1984). This suggests that OTR may be responsible for the induction of uterine activity during pregnancy but the function of this activity is unclear.…”

Section: Figurementioning

confidence: 98%

Regulation of oxytocin receptor in the placentome capsule throughout pregnancy in the ewe: the possible role of oestradiol receptor, progesterone receptor and aromatase

Leung

Reynolds²,

Wathes³

1998

Journal of Endocrinology

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The hormonal regulation of uterine oxytocin receptors (OTR) during the establishment of pregnancy and at parturition has been studied extensively, but little information is available during mid-pregnancy. This study investigated the localisation of OTR mRNA in the ovine placentome throughout gestation and related this to expression patterns for the putative regulatory agents aromatase, oestradiol receptor, progesterone receptor and oxytocin. Placentomes were collected at regular intervals throughout pregnancy for in situ hybridisation analysis and immunocytochemistry (oestradiol receptor only). Results were quantified by optical density measurements of autoradiographs. Progesterone receptor mRNA was localised to the caruncular tissues on day 30 but became undetectable by day 34. Aromatase mRNA appeared in the fetal villi at days 34-40, with concentrations peaking at days 52-55 and again at days 132-137. Oestradiol receptor mRNA was localised to the caruncular tissues from days 13 to 30 and found in the maternal villi and placentome capsule from days 45 to 70. Oestradiol receptor protein was barely detectable in either tissue. OTR mRNA was localised to the placentome capsule at days 34-40, remaining high at day 45 and declining to basal levels by days 132-137. Oxytocin mRNA was not detected in the placentome. In conclusion: (1) progesterone acting via its receptor may suppress the expression of aromatase and OTR in early pregnancy; (2) the up-regulation of OTR expression in the capsule may not involve the oestradiol receptor; (3) there is a differential regulation between different regions of the uterus as the increase in the placentome capsule occurs at a time when concentrations in the rest of the endometrium and myometrium remain low; (4) oestradiol receptor expression in the placentome may be regulated at the translational level; and (5) there is no local production of oxytocin in the sheep placenta. The role of OTRs in the capsule during mid-pregnancy remains to be determined.

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“…Laxative effects were determined by gross estimation of stool consis tency. Effects on intestinal motility were described in terms of changes in both the MMC pattern (ileum) and basal activity (spiral colon) according to the liter ature [22], Effects on uterocervical motility were de scribed in terms of changes in the pregnancy activity pattern [20].…”

Section: Design O F the Studymentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Garcia‐Villar¹

1988

Pharmacology

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The effects of sennosides on uterine motility were evaluated by electromyography in healthy adult ewes between day 70 and 120 of pregnancy to assess possible disturbances of the physiological pattern of contractility and eventual risks in pregnancy maintenance. At this stage of pregnancy, the ovine genital tract presented motility episodes of 6–8 min duration occurring at approximately hourly intervals. A dose-range study (10–160 mg/kg intracolonically) in 2 ewes showed that diarrhea was systematically obtained with doses > 20 mg/kg and was connected with a marked depression of both ileum and spiral colon motility. A standard dose of 60 mg/kg administered intracolonically 1–3 times at 7- to 10-day intervals to 12 ewes was used in the uterus studies. The experiments showed that sennosides did not stimulate uterine motility in the pregnant ewe, but slightly depressed it in some ewes. Cervix motility was never influenced. Intolerance of the drug was observed in half of the animals resulting mainly in anorexia or weakness and confirming a specific toxicity of senna in ruminants which is not known from other species. These effects were not related to uterine motility and pregnancy maintenance was normal in all ewes.

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

Cited by 32 publications

References 22 publications

Patterns of electrical propagation in the intact pregnant guinea pig uterus

Patterns of electrical propagation in the intact pregnant guinea pig uterus

Regulation of oxytocin receptor in the placentome capsule throughout pregnancy in the ewe: the possible role of oestradiol receptor, progesterone receptor and aromatase

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

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