Membrane potential and ionic content in pregnant and non‐pregnant rat myometrium

Casteels, Rik; Kuriyama, Hiroshi

doi:10.1113/jphysiol.1965.sp007591

Cited by 141 publications

(118 citation statements)

References 40 publications

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“…The electrical activity in the control situation was similar to that described by Casteels & Kuriyama (1965). The resting membrane potential was -55.1 ± 2.2 mV (n = 4).…”

Section: Intracellular Microelectrode Recording With Tissue Stripssupporting

confidence: 57%

“…However, in the rat uterus, which was as sensitive to the relaxant actions of BRL 349165 as portal vein and trachealis, the rapid and complete abolition of phasic spasms by BRL 34915 (1O gM) was associated with a hyperpolarization of only 5 mV which raised the membrane potential to -60 mV. Based on measurements ofionic content or ionic fluxes, the calculated EK in the rat uterus is between -77 mV and -90 mV (Casteels & Kuriyama, 1965;Hamon et al, 1976). Mironneau & Savineau (1980) and Mironneau et al (1981) have described two components (fast and slow) of the outward (K+) current in rat myometrium using the double sucrose gap technique.…”

Section: Discussionmentioning

confidence: 99%

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The relaxant action of BRL 34915 in rat uterus

Hollingsworth

Amédée

Edwards

et al. 1987

British J Pharmacology

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1 BRL 34915 (0.04-1.3 tiM) caused concentration-dependent inhibition of spontaneous phasic spasms of the isolated uterus of the term pregnant rat and this effect was not antagonized by propranolol. Spasms evoked by low concentrations of KC1 (< 20 mM) were inhibited by BRL 34915 but those evoked by higher concentrations ( >40 mM) were unaffected.2 In experiments using extracellular electrical recording, BRL 34915 (1O fM) selectively inhibited oxytocin-induced phasic spasms and the associated spike activity but had little effect on the tonic component of the spasms. BRL 34915, as an inhibitor of phasic spasms to oxytocin (0.2 nM), was antagonized by procaine (0.3 and 1 mM). 3 BRL 34915 (10 EM) did not inhibit Ca2+-induced spasm of saponin-skinned thin myometrial strips.4 Intracellular microelectrode recording from myometrial strips showed that BRL 34915 (10I jM) inhibited action potentials and phasic spasms in the presence of oxytocin (0.2 nM) and produced a hyperpolarization of 5 mV. 5In single myometrial cells under current or voltage clamp, BRL 34915 (0I jAM) had no effect on action potentials and inward current in Ca2+-or Ba2+-containing media in the presence of tetraethylammonium, 4-aminopyridine and .caesium chloride. In the absence of these K+-channel inhibitors, BRL 34915 had no effect on resting membrane potential, membrane resistance, action potentials, inward current or outward current.6 BRL 34915 (1 or 1O IM) had no effect on '8Rb efflux from myometrial strips. 86Rb efflux was increased by oxytocin (0.2 and 20 nM). 7 The relaxant profile of BRL 34915 in the rat uterus is similar to that described for other smooth muscles where an action to open membrane K+-channels has been proposed. BRL 34915 inhibited spike production but produced only a small hyperpolarization without a detectable increase in 86Rb efflux. Membrane resistance and transmembrane currents were unaffected. These results suggest that in the uterus the effects of BRL 34915 may be restricted to K+-channels involved in the production of pacemaker activity.

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“…The electrical activity in the control situation was similar to that described by Casteels & Kuriyama (1965). The resting membrane potential was -55.1 ± 2.2 mV (n = 4).…”

Section: Intracellular Microelectrode Recording With Tissue Stripssupporting

confidence: 57%

Section: Discussionmentioning

confidence: 99%

The relaxant action of BRL 34915 in rat uterus

Hollingsworth

Amédée

Edwards

et al. 1987

British J Pharmacology

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show abstract

“…It has been shown that spike potential dominates in the longitudinal muscle of rat uterus throughout the pregnancy stage (CASTEELS and KURIYAMA, 1965;KURIYAMA and SUzUKI, 1976a;OSA and FUJINo, 1978), whereas slow potential dominates in the t~ircular muscle during midpregnancy, and spike potentials Vol. 34, No.…”

Section: Discussionmentioning

confidence: 99%

Effects in vitro of progesterone and estradiol-17.BETA. on the contractile and electrical responses in rat myometrium.

Osa

Ogasawara

1984

Jpn.J.Physiol

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Uterine longitudinal and circular muscles from pre-and postterm rats were studied in vitro for their contractile and electrical activities under the influence of 20-100 ,uM progesterone, 20 ,uM estradioll7R, or 20 ,uM stilbestrol. Uterine longitudinal or circular muscle strips were irrigated by Krebs solution at 37°C containing one of the hormones mentioned above, dissolved by the use of ultrasonic wave. Muscle contractions were recorded by a force displacement transducer, and electrical activities of the muscle membrane were studied using an intracellular microelectrode. At diestrus and Day 14 of pregnancy, progesterone depressed the contractions of longitudinal muscle. At pre-term, progesterone potentiated the contractions and prolongated the membrane burst discharge of longitudinal muscles, while estradiol inhibited their contractions and suppressed spike activities. At the same stage of pregnancy, both progesterone and estradiol inhibited contractions of circular muscles. At post-partum, progesterone potentiated and then depressed longitudinal muscles, while estradiol inhibited their contractions. At this stage, both progesterone and estradiol inhibited contractions of circular muscles, although vigorous spike discharges were observed. Stilbestrol depressed contractions of both longitudinal muscles from diestrus rats and longitudinal ileal muscles from a guinea pig. In view of these findings, it was deduced that these ovarian hormones exert dual action on the uterine muscle in vitro, one through changes in the membrane activity and the other through dissociation of excitation-contraction coupling.

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“…Mechanical records traced by lower beam were made for muscle strips which were prepared along or transversly to the longitudinal axis of the uterine horn, so that the force generation of the muscle cells belonging to the longitudinal or circular muscle layers respectively was represented (OSA, 1974). As has been shown by previous investigators (MARSHALL, 1959;CASTEELS and KURIYAMA, 1965;OHASHI, 1970;ABE, 1971), the spontaneous electrical activity of the rat longitudinal muscle showed a train discharge of spike potentials supermounted on a slow potential, the membrane potential ranging between 50-60 mV The microelectrodes were advanced from the serosal or endometrial side of the strips for penetrating the longitudinal or circular muscles, respectively. The strips were obtained from the same pregnant rat near term.…”

Section: Resultsmentioning

confidence: 99%

Inhibitory Action of Human and Rat Placental Extracts on Myometrial Activities of Mouse and Rat

Osa¹,

Katase²,

Shibata

1974

Jpn.J.Physiol

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Summary Effects of placental extract (and perfusate) obtained from humans or rats were studied by recording the electrical and mechanical activities of pregnant rat and mouse myometria. 1) Membrane potential of circular muscle cells of pregnant rat myometrium ranged between 50-60 mV. Slow potentials amounting 20-30 mV dominated the circular muscle cells in contrast to spike potentials in the longitudinal cells.2) The placental extract (as well as rat uterine perfusate) reduced the magnitude of spontaneous contractions of myometrial strips of mouse and rat. The inhibitory effect on contractile response became more pronounced when Mg ions were present in the bathing media. The extracts did not cause a significant change in the membrane potential or action potential discharge, but the compound action potential recorded extracellularly was depressed.3) The extracts potentiated the mechanical response, when the myometrial tissue from pregnant animals was treated with fl-blocking agent (10-7g/ml propranolol) or with bretylium (10-5g/ml). 4) It was argued that placenta and endometrium of the pregnant animal release bioactive substances including a certain inhibitory agent which may cause the depressant effect on the conducting mechanism of excitation, possibly through an indirect action in releasing the endogenous catecholamines.Aside from the primary action of placenta as the locus of exchange of gases, nutrients and wastes between fetal and maternal bodies, it is also known to produce several bioactive substances including hormones and antigens.

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Membrane potential and ionic content in pregnant and non‐pregnant rat myometrium

Cited by 141 publications

References 40 publications

The relaxant action of BRL 34915 in rat uterus

The relaxant action of BRL 34915 in rat uterus

Effects in vitro of progesterone and estradiol-17.BETA. on the contractile and electrical responses in rat myometrium.

Inhibitory Action of Human and Rat Placental Extracts on Myometrial Activities of Mouse and Rat

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