In vivo myometrial activity during early pregnancy and pseudopregnancy in the rats

Linda H. Crane, Len Martin

Research output: Contribution to journalArticleResearchpeer-review

21 Citations (Scopus)

Abstract

Video-laparoscopic studies in early pregnant and pseudopregnant rats showed large changes in frequency, direction of propagation and nature of myométrial contractions. Day 2 patterns of activity were essentially the same as in unmated animals at the equivalent stage of the cycle. From Days 3 to 5 there was a large increase in longitudinal and circular contractions propagating towards the oviduct, circular contractions making the greatest contribution. This circular activity may be important in retaining and spacing embryos. Circular contractions propagating towards the cervix showed smaller increases and there was a transient diminution in the frequency of longitudinal contractions in this direction on Day 5. In pregnant rats, the frequency of discrete contractions declined on Days 6-7. However, circular tone appeared to be increased and uteri showed dramatic twisting and curling, apparently due to resistance to the shortening imposed by longitudinal contractions. None of the major changes in activity appeared to be caused by embryos, because they were seen in pseudopregnant rats and, after embryo implantation, in both horns of unilaterally pregnant rats. The earliest divergence from the activity patterns of unmated rats occurred when progesterone levels first increased significantly above those of the undisturbed oestrous cycle, suggesting that progesterone has a major influence on myométrial activity. The complexity of the changes in activity raises questions about other regulatory factors, particularly in regard to coordination between the circular and longitudinal muscle layers. Anomalous results from pregnant, unilaterally pregnant, and pseudopregnant animals on Day 7 suggested that embryos exert systemic effects on myométrial activity.

Original languageEnglish
Pages (from-to)233-244
Number of pages12
JournalReproduction, Fertility and Development
Volume3
Issue number3
DOIs
Publication statusPublished - 1 Jan 1991
Externally publishedYes

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Pseudopregnancy
pseudopregnancy
pregnancy
Pregnancy
rats
embryo (animal)
Embryonic Structures
Progesterone
progesterone
embryo implantation
Oviducts
cervix
Horns
oviducts
Cervix Uteri
shortenings
estrous cycle
uterus
Uterus
animals

Cite this

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title = "In vivo myometrial activity during early pregnancy and pseudopregnancy in the rats",
abstract = "Video-laparoscopic studies in early pregnant and pseudopregnant rats showed large changes in frequency, direction of propagation and nature of myom{\'e}trial contractions. Day 2 patterns of activity were essentially the same as in unmated animals at the equivalent stage of the cycle. From Days 3 to 5 there was a large increase in longitudinal and circular contractions propagating towards the oviduct, circular contractions making the greatest contribution. This circular activity may be important in retaining and spacing embryos. Circular contractions propagating towards the cervix showed smaller increases and there was a transient diminution in the frequency of longitudinal contractions in this direction on Day 5. In pregnant rats, the frequency of discrete contractions declined on Days 6-7. However, circular tone appeared to be increased and uteri showed dramatic twisting and curling, apparently due to resistance to the shortening imposed by longitudinal contractions. None of the major changes in activity appeared to be caused by embryos, because they were seen in pseudopregnant rats and, after embryo implantation, in both horns of unilaterally pregnant rats. The earliest divergence from the activity patterns of unmated rats occurred when progesterone levels first increased significantly above those of the undisturbed oestrous cycle, suggesting that progesterone has a major influence on myom{\'e}trial activity. The complexity of the changes in activity raises questions about other regulatory factors, particularly in regard to coordination between the circular and longitudinal muscle layers. Anomalous results from pregnant, unilaterally pregnant, and pseudopregnant animals on Day 7 suggested that embryos exert systemic effects on myom{\'e}trial activity.",
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In vivo myometrial activity during early pregnancy and pseudopregnancy in the rats. / Crane, Linda H.; Martin, Len.

In: Reproduction, Fertility and Development, Vol. 3, No. 3, 01.01.1991, p. 233-244.

Research output: Contribution to journalArticleResearchpeer-review

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