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KMID : 0378019660090070085
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New Medical Journal
1966 Volume.9 No. 7 p.85 ~ p.98
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The Sensitivity of Pregnant Rabbit Uteri to Epinephrine and Norepinephrine and Uterine Cateeholamine Content
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Abstract
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It has been known that norepinephrine and epinephrine, a neurohormonal transmitter, is synthesized and stored at the adrenergic nerve ending and that the uterus receives adrenergic terminals from the mesenteric ganglia. Many clinical studies to evaluate the action of ,´these catecholamines in the pregnant uteri have been carried out since 1925 when Rucker first reported the diminished uterine contractions in the laboring patient by the use of epinephrine in combination with novocaine. Two years later, Bourne and Burn confirmed the finding of decreased uterine contractions in labor following an intravenous drip of epinephrine, and Rucker also found that the injection of adrenaline causes a cessation of the uterine contractions and a relaxation of the constriction ring. Many investigators such as Rudolph and Ivy(1930), Ivy(1931), Irvins(1936), Titus(1937), Gunn(1942) and Garret(1954) have reported that epinephrine inhibits uterine contractions during pregnancy.
On the contrary, Woodbury, Hamilton and Torpin(1938) reported that the injection of epinephrine stimulates the uterine contraction. Woodbury and Abru (1944) stressed that the effect of epinephrine on the uterus is entirely depend upon its concentration; in low concentration the uterine contractions are inhibited whereas in high concentration they are stimulated. Kaiser and Harris(1950) confirmed the findings of Woodbury in 140 pregnant women. Telko(1960) reported that coordinated contractions can be produced by injection of norepinephrine and seems to be more effective on uterine contractions than oxytocin. In recent years, Pose et al. have reported that the intravenous infusion of 1-epinephrine in labor showed a decrease in the intensity of the uterine contractions, and infusion on the 1-norepinephrine in labor produced a clear increase in the contractility of the uterus and the induced contractility had a significantly different pattern from the spontaneous or oxytocin-induced ones. Cha(1965) has found that the catecholamine concentration of the uterus become reduced during pregnancy, particularly at the placental site, and a small amount of norepinephrine(10´7M) inhibits and a large amount stimulates the uterine activity whereas epinephrine always stimulates uterine activity regardless the amount. It is clear that many controversial opinions exist about the effect of epinephrine and norepinephrine on the pregnant uterus and there seems to be some relation between uterine catecholamine content and pregnancy. Therefore, the present study was undertaken to investigate uterine catecholamine content and uterine sensitivity to epinephrine and norepinephrine during pregnancy.
Materials and Methods
The experiments were conducted on the adult, female, albino rabbits subdivided into groups of 1160 mug/uterus.
4. Reserpine-treated: The sensitivity of the uterine segments prepared from the late pregnancy rabbits treated with repserpine (3 mg/kg intraperitoneally 24 hours before sacrifice) to the catec holamines was diminished in general_ A stimulating effect did´ occur only by a higher concentration (more than 10-6 M) of the catechloamines while an inhibitory action was observed by the lower concentration. This sensitivity showed a pattern similar to the early pregnancy. The uterine catecholamines in this group were markedly reduced, particularly so for the norepinephrine content.
Summary
The uterine catecholamine concentration which is present in considerably high level in normal uterus was started to decrease in the early pregnancy, reached the lowest level in the mid.-pregnancy and then started to increase again in the late pregnancy when the total catecholamine content became the highest level of all. This increase of catecholamine in late pregnancy was chiefly due to the increase of norepinephrine. on the other hand, the effect of catecholamine on the uterine activity was first inhibitory in the early pregnancy but became gradually stimulative as the pregnancy progressed. This stimulating action on the uterine motility was found to occur through the action of norepinephrine.
It is suggestive that uterine motility may be related to the catecholamine content, especially norepinephrine, in the uterus.
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