Spatial and temporal variations in local spike propagation in the myometrium of the 17-day pregnant rat

Lammers, Willem J; Arafat, Kholoud; El-Kays, Ahmad; El-Sharkawy, T. Y.

doi:10.1152/ajpcell.1994.267.5.c1210

Cited by 35 publications

(74 citation statements)

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“…As also indicated in previous studies (8,9,19), the rat myometrium shows a relatively stable pattern of burst activity interspaced with a period of quiescence. In the guinea pig uterus, however, in vitro, there does not seem to be any regularity in frequency or type of contraction.…”

Section: Discussionsupporting

confidence: 80%

“…The electrophysiology experiments were performed similar to those published previously (17,19). In summary, eight virgin Wistar rats were placed with a male overnight, and pregnancy was dated the next morning if sperm cells were observed in the vaginal lavage as day 0 of gestation.…”

Section: Methodsmentioning

confidence: 99%

“…The electrical activity in the uterus is characterized by bursts of spiking activity interspaced with periods of quiescence (6,16,19,25). Recordings with several to large numbers of extracellular electrodes have shown that these spikes (action potentials) propagate through the myometrium from cell to cell through the presence of gap junctions (10,11,26,28,35).…”

mentioning

confidence: 99%

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The location of pacemakers in the uteri of pregnant guinea pigs and rats

Lammers

Stephen

Al-Sultan

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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The pregnant uterus is a smooth muscle organ whose pattern of contraction is dictated by the propagation of electrical impulses. Such electrical activity may originate from one or more pacemakers, but the location of these sites has not yet been determined. To detect the location of the pacemaker in the gravid uterus, two approaches were used: 1) determine the site from where the contraction started using isolated uteri from the pregnant guinea pig, and videotape their contractions; and 2) record, in isolated uteri from pregnant term rats, with 240 extracellular electrodes simultaneously, and determine where the electrical bursts started. In both the contractile and electrophysiological experiments, there was not a single, specific pacemaker area. However, most contractions (guinea pig 87%) and bursts (rat 76%) started close to the mesometrial border (mean 2.7 ± 4.0 mm SD in guinea pigs and 1.3 ± 1.4 mm in rats). In addition, in the rat, most sites of initiations were located closer to the ovarial end of the horn (mean distance from the ovarial end 6.0 ± 6.2 mm SD), whereas such an orientation was not seen in the guinea pig. In both guinea pig and rat uteri at term, there is not one specific pacemaker area. Rather, contractile and electrical activity may arise from any site, with the majority starting close to the mesometrial border. Furthermore, in the rat, most activities started at the ovarial end of the horn. This may suggest a slightly different pattern of contraction in both species.

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Section: Discussionsupporting

confidence: 80%

Section: Methodsmentioning

confidence: 99%

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The location of pacemakers in the uteri of pregnant guinea pigs and rats

Lammers

Stephen

Al-Sultan

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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“…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 myometrium, but a few studies have recorded from a limited number of electrodes in the whole intact myometrium in vivo.…”

mentioning

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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“…Due to a lack of evidence [19], many authors concluded that no classical linear propagation of single APs, similar to the myocardium, could be assumed for the myometrium, and that only a global propagation of the whole burst envelop could be measured [19], [20]. However, more recently, extensive measurements of the electrical activity of the guinea pig uterus using a grid of extracellular electrodes clearly demonstrated that also for the myometrium, similarly to the myocardium, a linear propagation of single electrical spikes occurs and can be measured [12], [21], [22].…”

Section: A Backgroundmentioning

confidence: 99%