Specific features of smooth muscle cells recorded from the placental region of the myometrium of pregnant rats

Kanda, S; Kuriyama, Hirosi

doi:10.1113/jphysiol.1980.sp013115

Cited by 40 publications

(27 citation statements)

References 18 publications

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“…correlates well with studies in the rat myometrium in which weak potentials, slow propagations, and a shorter length constant were found in microelectrode recordings (16). In the pregnant cat, extracellular recordings performed in vivo and in vitro showed that the placental region was less excitable and showed little or no spontaneous action potentials (6).…”

Section: Discussionsupporting

confidence: 58%

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: Discussionsupporting

confidence: 58%

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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“…These occur in either Krebs, Tyrode, or Locke solutions (OsA et al, 1974;OSA and KATASE, 1975;OSA and FUJiNo, 1978;KANDA and KURIYAMA, 1980;KAWARABAYASHI and MARSHALL, 1981). It was also confirmed that noradrenaline causes excitatory effects in Day 21 preparations, and inhibitory effects in Day 22 preparations.…”

Section: Discussionsupporting

confidence: 51%

Changes in the adrenergic effects and membrane activity of the circular muscle of rat uterus during late pregnancy and postpartum.

Osa

Ogasawara

1984

Jpn.J.Physiol

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Circular muscle strips of rat uterus were obtained in the morning on Days 21 and 22 of pregnancy, and on the first postpartum day. Changes in the effects of noradrenaline and isoprenaline due to pregnant stage and incubation period in vitro were investigated, taking the contractile response and membrane activity as indicators. Plateau potential was dominant in Day 21 and postpartum preparations, and spike potential on Day 22. Noradrenaline (3 x 10-7, 10-g M) caused excitation in Day 21 and postpartum preparations, whereas it caused inhibition in Day 22 preparations during early exposure to Krebs solution. When contractile potentiation was caused, plateau potential was prolonged, and when contractile depression was caused the plateau potential was suppressed. By incubation in vitro with Krebs solution, a transformation of the effect of noradrenaline from excitation to inhibition was caused in Day 21 preparations, and from strong to weak inhibition in Day 22 preparations. Isoprenaline of 3 x 10-10 M concentration markedly depressed the contractile response in Day 22 preparations, whereas 10-8 M isoprenaline was not enough to suppress the spontaneous contractions in postpartum preparations.

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“…The extent to which similar mechanisms occur in the myometrium remains to be determined. The electrical activity of myometrial cells from placental regions is suppressed compared with non-placental regions in the rat uterus (Kanda & Kuriyama, 1980) possibly due to locally acting placental progesterone (Csapo, 1961). It is possible, therefore, that the exposure of the myometrial expiants to the lower progesterone concentrations of the peripheral circulation might reduce an inhibitory action of this or any other hormones produced by intrauterine tissues, and lead to an increased frequency of contraction.…”

Section: Discussionmentioning

confidence: 99%

An in-vivo model to examine the electromyographic activity of isolated myometrial tissue from pregnant sheep

Lye¹,

Freitag²

1988

Reproduction

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Summary. Strips (2\m=.\5\ m=x\3\ m=. \ 5cm) of myometrium alone (MYO) or endometrium/ myometrium (ENDO/MYO) were removed from the pregnant horn of sheep (Day 110 of gestation) and transplanted to sites within the omental fat. These explants developed regular bursts of electromyographic (EMG) activity over a period of 7\p=n-\10 days, as well as a dose-dependent stimulatory response to oxytocin (50\p=n-\200 mU i.v.). The frequency (per 2 h) of EMG bursts in the MYO (5\m=.\3\ m=+-\ 0\m=.\2) and ENDO/MYO (5\m=.\2\ m=+-\ 0\ m=. \ 3) explants was significantly greater (P < 0\m=.\05) than that of the uterine myometrium (3\m=.\0 \ m=+-\ 0\m=.\1), while burst duration (min) in MYO (4\m=.\1\m=+-\ 0\ m=. \ 2) and ENDO/MYO (4\ m=. \ 1 \ m=+-\ 0\m=.\2)explants was significantly (P < 0\m=.\05) less than in the uterine myometrium (7\m=.\3\ m=+-\ 0\m=.\1). The EMG bursts were asynchronous between the explants and uterus, although systemic administration of oxytocin produced a synchronous burst of EMG activity in all three tissues. No differences in EMG activity or responsiveness were apparent between MYO and ENDO/MYO explants. Histological examination of the explant tissue revealed the presence of smooth muscle fibres regularly orientated into two layers; some loss of endometrial tissue was apparent in ENDO/MYO explants. To validate the mechanical integrity of this model we examined the in-vitro contractile activity of myometrial strips prepared from the explants. The strips developed regular spontaneous contractions and demonstrated a dose-dependent stimulation in response to the addition of oxytocin (10\m=-\10 to 10\m=-\4m) to the bath fluid. These results suggest that spontaneous contractures during pregnancy are probably not due to pulsatile release of stimulants into the systemic circulation, or the direct diffusion of stimulants from intrauterine tissues to the myometrium but are probably caused by factors within the myometrium itself.

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Specific features of smooth muscle cells recorded from the placental region of the myometrium of pregnant rats

Abstract: SUMMARYThe muscle membrane and contractile properties of placental and non-placental regions of pregnant and postpartum myometria of the rat were investigated.

Cited by 40 publications

References 18 publications

Patterns of electrical propagation in the intact pregnant guinea pig uterus

Patterns of electrical propagation in the intact pregnant guinea pig uterus

Changes in the adrenergic effects and membrane activity of the circular muscle of rat uterus during late pregnancy and postpartum.

An in-vivo model to examine the electromyographic activity of isolated myometrial tissue from pregnant sheep

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