Search results for "Uterine Contraction"
showing 9 items of 29 documents
Comparative study of the rat uterine smooth muscle relaxant activity of three bisbenzyltetrahydroisoquinolines with tetrandrine
1993
Abstract The relaxant activity of three bisbenzyltetrahydroisoquinolines—obaberine, popisonine and lindoldhamine—was examined in rat isolated uterus and their inhibitory potencies were compared with that of tetrandrine. All alkaloids tested relaxed KCl-depolarized rat uterus and totally or partially inhibited oxytocin-induced rhythmic contractions. The degree of methylation of the free phenolic hydroxy groups and the loss of one diarylether bridge influence the potency of relaxant action of these alkaloids. Only alkaloids with absolute configuration 1R,1′S or 1R1′R acted intracellularly, promoting relaxation of contractile responses induced by oxytocin or vanadate in a Ca2+-free medium.
Inhibition of calcium entry induced by cularines and isocrasifoline in uterine smooth muscle.
1991
Abstract The effects of nifedipine, papaverine and four benzylisoquinoline alkaloids (cularine, cularidine, celtisine and isocrasifoline) were studied in isolated rat uterus in order to clarify the mechanism of their relaxant action. All the compounds tested completely relaxed KCl-induced contractions and totally or partially inhibited oxytocin-induced rhythmic contractions. Only papaverine acted intracellularly, promoting relaxation of contractile responses induced by oxytocin or vanadate in a Ca 2+ -free medium. In spite of the structural relationship between papaverine and the other alkaloids, the mechanism of their relaxant action is not the same. The activities of cularine derivatives …
Inhibitory effects of okadaic acid on rat uterine contractile responses to different spasmogens
1997
In the present study, we examined the effects of okadaic acid, a selective inhibitor of type I and 2A protein phosphatases, on the mechanical responses evoked by oxytocin, K + - and Na + -modified solutions and ouabain in estrogen-primed rat myometrium. Oxytocin elicited a rapid, phasic contraction followed by rhythmic oscillations. The phasic response was partially resistant to the absence of external Ca 2+ . Okadaic acid (1 μM) and the L-type calcium channel blocker nifedipine (1 μM) abolished the oscillatory component and reduced the initial, phasic response to about 80% of the control response. High K + (60 mM) solution, ouabain (1 mM), K + -free medium and low Na + (25 mM) solution ind…
Selective inhibition of calcium entry induced by benzylisoquinolines in rat smooth muscle.
1992
Abstract The mechanism of relaxant activity of six benzylisoquinolines was examined in order to determine the minimal structural requirements that enable these compounds to have either a non-specific action like papaverine or an inhibitory activity on calcium entry via potential-operated channels. All the alkaloids tested totally or partially relaxed KCl-depolarized rat uterus and inhibited oxytocin-induced rhythmic contractions. Only glaucine and laudanosine inhibited K+-induced uterine contractions more than oxytocin-induced uterine contractions. In Ca+-free medium, sustained contractions induced by oxytocin or vanadate were relaxed by the alkaloids tested except for glaucine and laudanos…
Relaxant effect of dopamine on the isolated rat uterus.
1988
The effect of dopamine was studied on the isolated uterus of diethylstilboestrol-treated rats. Dopamine, at concentrations (10(7)-10(-4) M) produced a concentration-dependent relaxation in the K+-depolarized rat uterus. On a molar basis, dopamine was about 500 times less potent than adrenaline in relaxing the uterus, the maximum degree of relaxation obtained with both drugs was the same. Pretreatment of the rats with reserpine (5 mg/kg) did not produce any modification of the dose-response curve to dopamine. Similarly, cocaine (3 x 10(-6) M) failed to modify the relaxant effect of dopamine. The dopamine induced relaxation was inhibited by propranolol (10(-9)-10(-7) M) in a dose-dependent ma…
Effect of histamine on the longitudinal and circular muscle of the oestrogen dominated rat uterus.
1993
The response of the longitudinal and circular myometrial strips to histamine was studied in oestrogen-treated rats. Histamine produced a dose-related inhibitory response in KCl-contracted longitudinal and circular uterine strips. Histamine was equipotent in producing the relaxant response but the maximal effect achieved in the longitudinal muscle was higher than the circular one. Ranitidine antagonized the histamine-induced relaxation with a similar dose ratio in both longitudinal and circular strips. Clemizole and reserpine treatment did not produce any modification of the dose-response curve to histamine. In the longitudinal and circular strips which were not preconstricted by KCl, neithe…
Response to dopamine agonists of the rat isolated uterus.
1993
1. Quinpirole did not produce any effect in isolated uterus from oestrogenized rats even when it is contracted by KCl (37 mM). 2. Fenoldopam produced a relaxant effect on rat isolated uterus contracted by KCl which was not significantly modified by SCH 23390. 3. Reserpine decreased the effect of the lowest doses of fenoldopam. In reserpinized rats, propranolol (10(-9), 10(-8), 10(-7) M) antagonized the effect of the lowest doses of fenoldopam and neither SCH 23390, sulpiride nor ranitidine modified the effect of fenoldopam. 4. The results confirm our previous finding that DA1-receptors are not functional in our preparation. The effect of fenoldopam was partially due to a catecholamine-relea…
Umbilical artery blood flow velocity waveforms during variable decelerations of the fetal heart rate
1991
Blood flow velocities of the umbilical arteries were measured by Doppler ultrasonography during variable decelerations of the fetal heart rate. The flow velocity waveforms, being normal between uterine contractions, showed either an unchanged flow velocity waveform with an exclusive fetal heart rate effect on end-diastolic velocities or a rapid change to absent and reverse diastolic flow during the decelerations, indicating an abrupt increase in placental resistance with a halt in placental perfusion. Computer-aided reconstruction of the fetal heart rate curve revealed the exact temporal relationship between the reduction of umbilical artery perfusion and deceleration of fetal heart rate. W…
Effects of Methoxamine on Spontaneous Uterine Activity and Blood Flow of the Rat Uterus ‘in vivo’
1992
The vascular (blood pressure, heart rate and peripheral blood flow) and uterine (spontaneous motility) responses to intravenous methoxamine were studied in anaesthetized rats pre-treated with diethylstilboestrol. Methoxamine produced an increase (0.5-2 mg/kg) or did not modify (0.01 and 3 mg/kg) spontaneous uterine motility. The alpha 1-agonist also induced a hypertensive effect (0.1-3 mg/kg) accompanied by bradycardia at the highest doses, and a decrease in blood flow significantly greater in intestinal than uterine tissues. These effects were abolished by prazosin. The uterine action of methoxamine in vivo appears to result from the balance between myometrial alpha 1-excitatory effect and…