Electrophysiological Comparison of the Action of Oxytocin and Carbachol on Pregnant Mouse Myometrium

Osa, Takuro; Taga, Fukutaro

doi:10.2170/jjphysiol.23.81

Cited by 17 publications

(12 citation statements)

References 22 publications

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“…About 10-5 to 10-4 g/ml of carbachol, the value varying by tissues , was needed to cause peak depolarization of about -20 mV. With this dose, the muscle strip undergoes sustained contracture (OsA and TAGA, 1973). It was found in the present experiment that the circular strip was more insensitive to carbachol .…”

Section: Resultsmentioning

confidence: 47%

An Interaction Between the Electrical Activities of Longitudinal and Circular Smooth Muscles of Pregnant Mouse Uterus

Osa

1974

Jpn.J.Physiol

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Section: Resultsmentioning

confidence: 47%

An Interaction Between the Electrical Activities of Longitudinal and Circular Smooth Muscles of Pregnant Mouse Uterus

Osa

1974

Jpn.J.Physiol

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“…Krnjevi6' (1974) has suggested a unifying hypothesis, applicable to all these cells, of a reduction in outward K current which has the dual effect of delaying repolarization following a spike and reducing the potential in the interspike interval. Certainly the actions of acetylcholine on ileum and on neurones are superficially very similar, but acetylcholine produces a large increase in conductance in smooth muscle (Bolton, 1972b;Magaribuchi, Ito & Kuriyama, 1973;Osa & Taga, 1973;Biilbring & Szurszewski, 1974) while it reduces the conductance of neuronal membrane (loc. cit.).…”

Section: Voltage Clamp Of Smooth Muscle 195mentioning

confidence: 99%

“…Thus, a spike may arise in a remote or deep part of the muscle (Osa & Taga, 1973) but, upon propagating to the region of recording its duration is greatly increased and its size reduced by the increased conductance. An argument against this 176 T.B.BOLTON VOLTAGE CLAMP OF SMOOTH MUSCLE hypothesis is that normal spikes can sometimes be recorded as taking off at the peak of the slow wave ( fig.…”

Section: Introductionmentioning

confidence: 99%

Effects of stimulating the acetylcholine receptor on the current‐voltage relationships of the smooth muscle membrane studied by voltage clamp of potential recorded by micro‐electrode.

Bolton¹

1975

The Journal of Physiology

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SUMMARY1. A double sucrose-gap voltage-clamp technique is described for use on smooth muscle strips longer than about 2 mm. It involves intracellular recording by microelectrode of the membrane potential of a narrow region of the strip ('node') sandwiched between two streams of deionized sucrose solution. Current was passed into the node across one or both sucrose streams.2. Preliminary experiments in which potential was recorded intracellularly at two points during polarization of a 'short cable' preparation, formed by folding over a strip of smooth muscle, suggested that a node width of less than 0O15 mm was needed to achieve uniform potential during inward current flow. However, when node width between sucrosegaps was reduced to 05 mm, spontaneous electrical activity was lost, and below 05 mm spike threshold was raised and the regenerative spike became graded. The currents flowing during the application of rectangular voltage-clamp command potentials were described.3. Using taenia smooth muscle it was shown by recording with a second, independent micro-electrode that potential was not uniform for up to 200 ms or more following a step change in potential under voltage-clamp in nodes 004-0 5 mm wide where current was passed across both sucrose gaps. However, reasonably uniform nodal potentials were obtained using ramps with relatively slow rates of rise (25 mV/s). 4. Using such slow ramp commands under voltage clamp, the effects of carbachol on the current-voltage relationship of longitudinal muscle of ileum and taenia were studied in hypertonic solution.5. In the presence of carbachol (10-to 10 g/ml.) additional inward current flowed across the membrane (in some experiments an equilibrium potential was observed at which this current reversed direction). The magnitude of this additional current was linearly related to potential at potentials negative to the resting potential. At potentials positive to the resting membrane potential, this additional current increased with depolarization over the range -40 to -10 mV; in ileum the effect of this additional inward current on the current-voltage relationship was to produce a region of net inward current where before, in the absence of carbachol, a net outward current existed. In taenia the additional inward current flowing in the presence of carbachol was too small to produce a region of net inward current; thus carbachol produced regenerative slow oscillations of potential (slow waves) in ileum but not in taenia.6. These results support a previous suggestion that activation of the acetylcholine receptor of ileal smooth muscle produces an additional inward current in the membrane which increases with depolarization and is responsible for the regenerative slow waves seen when muscarinic stimulants are applied. A similar effect apparently operates in taenia but the additional inward current is too small to produce regenerative slow waves.

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“…Studies of the rat, rabbit and mouse isolated myometrium demonstrate that, at low concentrations, oxytocin has the following properties [10,12,22,25] At high oxytocin concentrations, large intracellular depolarizations may occur [22] which could lead to suppression or block of spikes, whereas contractile tone remains elevated [4,5,18]. Furthermore, there are reports that at these high oxytocin concentrations, electrical and mechanical activity are no longer correlated, at least at the intracellular level [24].…”

Section: Introductionmentioning

confidence: 99%

The effects of oxytocin on the pattern of electrical propagation in the isolated pregnant uterus of the rat

Lammers

Stephen

Hamid

et al. 1999

Pfl�gers Archiv European Journal of Physiology

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In the isolated pregnant myometrium of the rat, the pattern of propagation was investigated by recording simultaneously from 240 different extracellular sites while the contraction of the tissue was recorded isometrically. Analysis of all recorded electrograms allowed the two-dimensional spread of activity in the myometrium to be reconstructed. From these activation maps, the conduction velocities were measured in the longitudinal, oblique and transversal directions. At low concentrations (10(-9 )and 5x10(-9) M), oxytocin significantly increased the frequency and duration of electrical bursts and the average spike intervals, without affecting the homogeneity of action potential propagation, concomitant with a significant increase in the amplitude of contractions. At high concentrations (10(-8) and 5x10(-8) M), oxytocin induced conduction blocks and the size of inexcitable areas was increased, concomitantly with an increase in muscle contractures. In contrast, the conduction velocities in the longitudinal, oblique and circular directions were not influenced by oxytocin at any concentrations.

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Electrophysiological Comparison of the Action of Oxytocin and Carbachol on Pregnant Mouse Myometrium

Cited by 17 publications

References 22 publications

An Interaction Between the Electrical Activities of Longitudinal and Circular Smooth Muscles of Pregnant Mouse Uterus

An Interaction Between the Electrical Activities of Longitudinal and Circular Smooth Muscles of Pregnant Mouse Uterus

Effects of stimulating the acetylcholine receptor on the current‐voltage relationships of the smooth muscle membrane studied by voltage clamp of potential recorded by micro‐electrode.

The effects of oxytocin on the pattern of electrical propagation in the isolated pregnant uterus of the rat

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