Uterotonic properties of the methanol extract of Monechma ciliatum.

The oxytocic activity of the hot methanol extract (HME) of the leaves of Monechma ciliatum was compared with other uterine stimulants like ergometrine, oxytocin, 5-hydroxytryptamine (5-HT), acetylcholine (ACh) and prostaglandins (PGs) E2 and F2alpha (PGE2 and PGF2alpha) in the presence of some antagonists in an attempt to explain the mechanism of action of the extract. The effects of the reference drugs on uteri isolated from rats pretreated with HME for 2 weeks were also observed. Atropine blocked the effect of ACh and partially blocked those of HME while L-366-948 blocked only the effect of oxytocin. Indomethacin inhibited the effects of HME as well as all the other drugs, except the PGs and ACh. D-600 blocked the effect of all the drugs including HME. Methysergide antagonised only the effect of 5-HT and partially blocked ergometrine. Prolonged treatment altered the uterine musculature and the activity profile of the reference drugs. These results suggest that the HME may be acting by more than one mechanism to contract the uterus and explains the mechanism of the anti-implantation activity of the plant.