Summary
The influence of oxytocin on the electrical and mechanical activity of uterine smooth muscle strips was studied under voltage-clamp conditions.
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1.
At a concentration of 0.1 mU/ml, oxytocin caused a slight depolarization of the resting potential and also increased the amplitude of the action potential. The maximal frequency of the rhythmic activity, which can be produced by depolarizing current pulse, is increased by about 20%.
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2.
Oxytocin increased the peak of the inward current without modification of the reversal potential. This effect is enhanced in a sodium-free solution. With oxytocin the steady-state inactivation of the inward current is not modified and the increase in the current intensity can be related to an increase in the maximal conductance. The amplitude of the outward current is not affected.
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3.
The first component (phasic-like) of the contractile response obtained for brief depolarizations is increased by oxytocin. This effect may be explained by the increase in the intensity of the inward current. The second component (tonic-like) of the contraction associated with long-lasting depolarizations and obtained in manganese-containing solution is not modified. The increased frequency of the rhythmic activity after oxytocin administration may also result in increased contractility by summation.
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References
Abe, Y.: Effects of changing the ionic environment on passive and active membrane properties of pregnant rat uterus. J. Physiol. (Lond.)214, 173–190 (1971)
Anderson, N. C.: Voltage clamp studies on uterine smooth muscle. J. gen. Physiol.54, 145–165 (1969)
Bedford, C. A., Challis, J. R. G., Harrison, F. A., Heap, R. B.: The role of oestrogens and progesterone in the onset for parturition in various species. J. Reprod. Fert.16, 1–23 (1972)
Bolton, T. B.: Effects of stimulating the acetylcholine receptor on the current-voltage relationships of the smooth muscle membrane studied by the voltage clamp of potential recorded by micro-electrode. J. Physiol. (Lond.)250, 175–202 (1975)
Casteels, R., Bremen, C., van, Mayer, C. J.: A study of the calcium distribution in smooth muscle cells of the guinea-pig taenia coli using La3+. Arch. int. Pharmacodyn.199, 193–194 (1972)
Casteels, R., Kuriyama, H.: Membrane potential and ionic content in pregnant and non-pregnant rat myometrium. J. Physiol. (Lond.)177, 263–287 (1965)
Gargouil, Y. M., Leoty, C., Poindessault, J. P., Raymond, G.: Evolution du courant initial global et de la contraction sur la fibre sino-auriculaire de grenouille. C. R. Acad. Sci. (Paris.)269, 1686–1689 (1969)
Hodgkin, A. L., Huxley, A. F.: A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. (Lond.)117, 500–544 (1952)
Imai, S., Takeda, K.: Actions of calcium and certain multivalent cations on potassium contracture of guinea-pig's taenia coli. J. Physiol. (Lond.)190, 155–169 (1967)
Johnson, E. A., Lieberman, M.: Heart: excitation and contraction. Ann. Rev. Physiol.33, 479–532 (1971)
Kao, C. Y., McCullough, J. R. Mc.: Ionic currents in the uterine smooth muscle. J. Physiol. (Lond.)246, 1–36 (1975)
Kleinhaus, A. L., Kao, C. Y.: Electrophysiological actions of oxytocin on the rabbit myometrium. J. gen. Physiol.53, 758–780 (1969)
Kuriyama, H.: The effect of progesterone and oxytocin on the mouse myometrium. J. Physiol. (Lond.)159, 26–39 (1961)
Leoty, C., Poindessault, J. P.: Effects and compensation of the series resistance in voltage-clamp experiments using double sucrose-gap technique. J. Physiol. (Lond.)233, 108–109P (1974)
Marshall, J. M.: Behaviour of uterine muscle in Na-deficient solution; effects of oxytocin. Amer. J. Physiol.204, 732–738 (1963)
Mironneau, J.: Excitation-contraction coupling in voltage clamped uterine smooth muscle. J. Physiol. (Lond.)233, 127–141 (1973)
Mironneau, J.: Voltage clamp analysis of the ionic currents in the uterine smooth muscle using the double sucrose gap method. Pflügers Arch.352, 197–210 (1974)
Mironneau, J., Lenfant, J.: Analyse des résponses électriques de la fibre musculaire lisse de l'utérus de ratte; mise en évidence d'un courant lent calcico-sodique. C. R. Acad. Sci. (Paris)272, 436–439 (1971)
Mironneau, J., Lenfant, J.: Activité électrique répétitive et courants transmembranaires du faisceau musculaire lisse de l'utérus; action de l'ocytocine. C. R. Acad. Sci. (Paris)274, 3269–3272 (1972)
Osa, T., Taga, F.: Electrophysiological comparison of the action of oxytocin and carbachol on pregnant mouse myometrium. Jap. J. Physiol.23, 81–96 (1973)
Ramon, F., Anderson, N., Joyner, R. W., Moore, J. W.: Axon voltage-clamp simulation. IV. A multicellular preparation. Biophys. J.15, 55–69 (1975)
Rougier, O., Vassort, G., Stämpfli, R.: Voltage clamp experiments on frog atrial heart muscle fibres with the sucrose gap technique. Pflügers Arch. ges. Physiol.301, 91–108 (1968)
Tarr, M., Trank, J. M.: An assessment of the double sucrose gap voltage clamp technique as applied to frog atrial muscle. Biophys. J.14, 627–643 (1974)
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Mironneau, J. Effects of oxytocin on ionic currents underlying rhythmic activity and contraction in uterine smooth muscle. Pflugers Arch. 363, 113–118 (1976). https://doi.org/10.1007/BF01062278
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DOI: https://doi.org/10.1007/BF01062278