Abstract
Aims: To investigate the effect of aqueous ethanolic leaf extract of this medicinal plant on isolated uterine smooth muscle strips of the rat and to determine its mechanism of action.
 Study Design: Laboratory-experimental design was used in this study.
 Place and Duration of Study: The study was carried out in the Department of Veterinary Physiology and Biochemistry of Michael Okpara University of Agriculture, Umudike, Nigeria, Department of Pharmacology and Toxicology of the Faculty of Pharmacy, University of Nigeria, Nsukka, and the Department of Veterinary Physiology and Pharmacology, University of Nigeria, Nsukka, Nigeria between June and October 2014.
 Methodology: Fresh leaves of Mucuna pruriens were identified and collected by a taxonomist from Nsukka, Nigeria. The leaves were then air dried and pulverized into powder. This was then subjected to cold extraction using petroleum ether (70-90) and 70% aqueous ethanol, after which the extract was left to dry at room temperature. Estrogenised uterine strips (12mm) were harvested from non-pregnant, sexually matured albino rats (180 g -250 g) and suspended in a 35ml organ bath containing Krebs’ physiological salt solution. The organ bath was connected to an isometric electronic force displacement transducer and a physiograph. Drugs such as Salbutamol, Isoprenaline, Adrenaline, Propranolol, Atipamezole and Prazosin were used as either agonists or antagonists to determine the mechanism of action of the extract. Atropine sulphate and Cyproheptadine were also used as test drugs. Concentrations of these drugs presented in the body of this work represent the final nutrient bath concentrations.
 Results: M. pruriens caused a dose -dependent increase in uterine muscle contraction with an EC50 of 0.88 mg/ml, n=4. The contraction was unaffected by atropine sulphate (0.042 µmol), but abolished by salbutamol (0.012-0.4 µmol), isoprenaline (0.06-0.23 µmol), and adrenaline (16 nmol). The uterine muscle contractions were enhanced by propranolol (1 µmol) in a dose- dependent manner. Prazosin (0.069-0.14 µmol) and atipamezole (3.3-13.7 nmol) were unable to abolish contractions stimulated by the extract. However, 0.2 µmol of cyproheptadine caused 80% suppression of the extract –induced uterine contraction
 Conclusion: It is concluded that aqueous ethanolic leaf extract of M. pruriens, has ability to cause uterine smooth muscle contraction hence, justifies its reported use traditionally as a uterine stimulant. This contraction is most likely exerted via the 5-HT receptor activation (activated by low concentrations of serotonin).
Highlights
Medicinal plants have proven to be very good therapeutic agents just like the orthodox drugs, but unlike the orthodox drugs, are said to exhibit only minimal or no side/ adverse effects [1]
Some datas generated were analyzed using student t-test and one-way Analysis of Variance (ANOVA) where necessary, and the results presented as mean ± standard error of the mean (SEM)
Non-cumulative concentrations of propranolol (0.5 - 3 μmol) introduced before a fixed concentration of M. pruriens (0.86 mg/ml), potentiated the frequency of spikes in the burst of uterine smooth muscle contractions induced by the extract in a dose-related manner (Fig. 4b)
Summary
Medicinal plants have proven to be very good therapeutic agents just like the orthodox drugs, but unlike the orthodox drugs, are said to exhibit only minimal or no side/ adverse effects [1]. Traditional medicine relies on the use of certain herbal plants and other remedies for beneficial effects during pregnancy, to induce labour, in the removal of retained placenta and management of post-partum bleeding [4]. Complications of pregnancies can be managed via the use of uterotonics or tocolytics. Tocolytic agents are drugs designed to inhibit myometrial contractions or relax the uterus [5]. The use of uterotonics have been recommended by WHO for prevention of postpartum haemorrhage during third stage of labour [7]. Though there is an array of information available on traditionally used herbs to treat gynecological problems [9,10], there is a need for continuous research to find new substances that are cost effective, readily accessible and without side effects
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