Antispasmodic Effect of Zataria multiflora Boiss. Leaf Extract on the Rat Uterus

Zataria multiflora Boiss. is used in Iranian traditional medicine to treat gastrointestinal disorders and menrrhalgia. The inhibitory effect of this herb on rat ileum contractions is also reported. The aim of this study was to investigate the effect of Zataria multiflora Boiss. hydroalcoholic leaf extract (ZHLE) on isolated rat uterus in presence of some known uterus stimulants. Pieces of virgin adult rat uterus were mounted in an organ bath containing Tyrode or De Jalon solutions. Uterus contraction was induced by KCl, oxytocin and BaCl₂ in presence and absence of certain concentrations of ZHLE. In the oxytocin studies, animals received an injection of oestradiol valerate (5mg/kg, S.C.) 24h prior to the experiment. ZHLE (0.125, 0.25, 0.5, 1 and 2 mg/ml) relaxed the uterus precontracted by KCl (60mM) in a dose-dependent manner (P<0.0001) and at 2mg/ml attenuated the BaCl₂ (4mM)-induced uterus contraction (P<0.001). The inhibitory effect of ZHLE on KCl-induced uterus contraction was unaffected by propranolol (1µM). In normal De Jalon solution, ZHLE (0.125, 0.25, 0.5, and 1mg/ml) reduced the oxytocin (10mU/ml)-induced contraction dose-dependently (P<0.0001) but in Ca²⁺-free De Jalon solution, the stimulatory effect of oxytocin was lesser nevertheless, the inhibitory effect of ZHLE was higher. In presence of atropine (0.5µM), acetylcholine (0.5µM) was failed to induce contraction but KCl (30mM) evoked contraction and the extract diminished the contractile response of KCl. The spasmolytic effect of extract (2mg/ml) on KCl-induced contraction was unaffected by naloxone (1µM). From the obtained results it may be concluded that, the ZHLE may induce the inhibitory effect through blockage of the voltage dependent calcium channels and releasing calcium from intracellular stores in rat uterus smooth muscle. The ineffectiveness of propranolol and naloxone on ZHLE inhibitory effect indicates that adrenergic and opioid agonist substance(s) does not exist in the extract. It seems that there is no anticholinergic substance(s) in the extract. The results support the usage of this plant in traditional medicine.