Pharmakologischen Untersuchungen am überlebenden Meerschweinchenuterus

XXII.—The Peripheral Innervation of the Uterus

The present investigation was undertaken to throw some light upon the nature and mode of action of the peripheral nervous mechanism of the uterus.

Previous work has demonstrated that the organ, like other viscera, has an autonomic action. That the uterus and vagina can function independently of the central nervous system has been shown both clinically and experimentally by Sir J. Y. Simpson (1), Goltz (2), Riemann (3), Rein (4), Kabierske and Heidenhain (5), Masius (6), and Kurdinowsky (7).

The nervous mechanism of the uterus may be divided into a central and a peripheral part.

In vitro determination of the mechanism of the uterine stimulatory effect of Newbouldia laevis

The uterine stimulatory effect of the ethanol leaf extract of Newbouldia laevis (Beauv.) Seemann ex Bureau (Bignoniaceae) was evaluated in the presence of some antagonists in vitro in an attempt to elucidate the mechanism of action of the extract. The extract was tested in the presence and absence of phentolamine (4.09 and 40.91 nM), diphenhydramine (4.45 and 44.47 nM), atropine (1.18 and 11.91 nM), and verapamil (2.03 and 20.35 nM). The effect of the antagonists on the extract and on oxytocin used as a reference drug in this study was evaluated. The EC(50) and E(max) were determined and statistically analyzed using one way ANOVA and Dunnett's post hoc test. There was no significant difference in the EC(50) and E(max) of the extract and oxytocin in the presence of phentolamine. Diphenhydramine and atropine significantly inhibited (p <0.01) the extract but both drugs had no effect on oxytocin. However, significant differences (p <0.01) were observed in the EC(50) and E(max) of the extract and oxytocin in the presence of verapamil. These results suggest that the leaf extract of N. laevis contracts the uterus by opening voltage-operated calcium channels and/or by activation of muscarinic receptors.

In vitro determination of the uterine stimulatory effect of the aqueous leaf extract of Ficus exasperata

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Ficus exasperata Vahl (Moraceae) are used by traditional healers in Southern Nigeria to arrest pre-term contractions and are also used as an abortifacient in some parts of Africa.

AIM OF STUDY

An earlier study on the aqueous leaf extract of Ficus exasperata (AET) showed that the extract at lower concentrations inhibited oxytocin-induced uterine contractions and at higher concentrations, stimulated uterine contraction. This study thus aims to determine, the possible mechanisms by which AET stimulates uterine contraction in vitro.

MATERIALS AND METHODS

The contractile effect of AET (5.0 x 10(-2) to 100 x 10(-2)mg/ml) and oxytocin (which was used as a reference drug) were examined in the presence of the following antagonists: atropine (1.18 and 11.91 nM); indomethacin (1.42 and 14.25 nM); verapamil (2.03 and 20.35 nM); phentolamine (4.09 and 40.91 nM), or diphenhydramine (4.45 and 44.47 nM). The EC(50) and E(max) were determined and statistically analyzed using one-way ANOVA and Dunnett post hoc test.

RESULTS

There was no significant difference in the EC(50) and E(max) of AET and oxytocin in the presence of atropine. Diphenhydramine and phentolamine significantly inhibited (p<0.01) the extract but both drugs had no effect on oxytocin. However, significant differences (p<0.01) were observed in the EC(50) and E(max) of AET and oxytocin in the presence of verapamil and indomethacin.

CONCLUSIONS

These results suggest that the stimulation of uterine contractility by AET may arise from the activation of histamine H(1)- and/or alpha-adrenergic receptors, interference with calcium channels and/or stimulation of prostaglandin synthesis in utero.

ACTION OF OUABAIN ON THE GUINEA-PIG ISOLATED UTERUS

Uterine activity in vitro was measured isometrically by integrating tension against time, and contractions were recorded on a kymograph using a servo-recorder. Ouabain caused a persistent contraction both of the spontaneously contracting and of the electrically stimulated uterus, the response depending upon the presence of calcium. After ouabain had induced a contraction of the spontaneously active uterus, relaxation to the baseline after washing out the ouabain was succeeded by a period of inactivity. Since the uterus could respond as usual to stimulation during this period, ouabain appeared to be selectively depressing spontaneous contractions. High concentrations of progesterone suppressed uterine activity and the response to ouabain. Ouabain reduced the susceptibility of the uterus to depression by anoxia.