Abstract:
Objective: To investigate the uterine smooth muscle relaxant property of the root extract of Cissampelos mucronata and relate it to its traditional use in the prevention of pre-term labour. Materials and methods: Phytochemical and pharmacological screenings were carried out using standard procedures. In addition to investigating the effects of the extract on non-gravid and gravid rat uterus, its effects on contractions induced by known uterine stimulants were assessed. The effects of the extract on the amplitude and frequency of contractions of gravid rat uterus were also determined. With the use of glibenclamide, an ATP-sensitive potassium channel blocker, the effect of the extract on potassium channel opening was studied. Result: Phytochemical constituents present in the root include carbohydrates, glycosides, sterols/triterpens, flavonoids, tannins and alkaloids. The extract relaxed the non-gravid rat uterus in a concentration- and time- dependent fashion. It also antagonized contractions evoked by serotonin, oxytocin, acetylcholine and prostaglandin E2 (known uterine spasmogens). The uterine relaxant effect of terbutaline (a selective β2-receptor agonist used as a tocolytic agent) was potentiated by the extract in a concentration-related manner while the contractions induced by propranolol (a non-selective β-receptor antagonist) were inhibited by the extract. The frequency and amplitude of contractions of the gravid uterine strips in the absence and presence of the extract were significantly different (p<0.05). Glibenclamide antagonized the uterine relaxant effect of the extract, an indication of possible participation of potassium channel in the actions of the extract. The contractions evoked by calcium chloride in uterine smooth muscles suspended in Ca2+-free K+-depolarizing solution were inhibited by the extract, suggesting that the activities of the extract may be non-specific in origin. Conclusion: Ethanolic root extract of C.mucronata displayed significant (p<0.05) relaxant activity on the isolated gravid and non-gravid rat uterine smooth muscles. The results justify the use of the plant in traditional medicine as a tocolytic (uterine relaxant) agent.
