Launaea taraxacifolia is used by the traditional health practitioners in Sokoto to ease labour pains and augment labour thereby facilitating child birth. This study examined the effect of the aqueous extract of the whole plant on isolated uterus from non-pregnant rats pre-treated with stilbestrol and from pregnant rats in late gestation. This was compared to the effects of uterine contraction agonists, namely; oxytocin, histamine and acetylcholine. The possible mechanism of uterotonic activity was investigated using antagonists such as piroxicam, mepyramine and atropine. The aqueous extract of L. taraxacifolia produced a dose-dependent uterotonic activity. In the stilbestrol treated non-pregnant uterus, the force generated at 400, 800 and 1600 mg/ml was 1.469, 1.624 and 1.793 times greater than the control, respectively. In the pregnant rat uterus, a dose of 400, 800 and 1600 mg/ml generated a force of contraction that was 1.36, 1.51 and 1.66 times greater than the control, respectively. When the relative potency was compared to oxytocin, the gold standard uterotonin, L. taraxacifolia at 1600 mg/ml was found to be 0.08 times more potent than 0.4 µg/ml oxytocin in the stilbestrol treated non-pregnant rat uterus. In the pregnant rat uterine strip however, oxytocin was 0.17 times more potent than 1600 mg/ml L. taraxacifolia. Pre-treating the tissue with either atropine or mepyramine before administering the extract showed an inhibitory effect while piroxicam completely abolished its uterotonic effect, showing a probable moderate stimulation of muscarinic and histamine receptors but majorly the oxytocin receptors by L. taraxacifolia. A preliminary phytochemical screening of the extract shows the presence of saponins, tannins, flavonoids and steroids. A dose of 2000 mg/kg/oral of L. taraxacifolia was found to be well tolerated in rats with no sign of toxicity. Thus, L. taraxacifolia contains phytochemicals with uterotonic properties thereby justifying its ethnobotanical use in easing labour.
Key words: Launaea taraxacifolia, uterotonic, labour, isolated uterus.
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