Spasmolytic Activity of Piper Nigrum Fruit Aqueous Extract on Rat Non-Pregnant Uterus

Black pepper (Piper nigrum) from Piperaceae and its main ingredient (piperine) reduces gastric emptying in rats. In Iranian traditional medicine, black pepper is used to relief the menorrhalgia in women. The aim of this study was to investigate the effect of black pepper fruit aqueous extract on non-pregnant rat uterus contractions and the mechanism(s) of its action. To prepare the extract, black pepper powder was added to boiling distilled water and then, solvent was evaporated. Uterus was dissected from non-pregnant adult rat (Wistar) and in De Jalon solution the tissue contractions were recorded isometrically under 1 g tension. The extract (0.125-2 mg/ml) reduced the uterus contractions induced by KCl (60 mM) and oxytocin (10 mU/ml) dose dependently (P<0.0001). The spasmolytic effect of extract on the KCl-induced contractions was not reduced by L-NAME (100 µM), phentolamine (1 µM) or naloxone (1 µM). However, propranolol (1 µM) reduced the extract activity (P<0.01–P<0.0001). In Ca2+free De Jalon solution with high potassium (60 mM), extract (0.0312-0.25 mg/ml) reduced the contractions induced by cumulative concentrations of CaCl2 (0.1-0.5 mM) dose dependently (P<0.05– P<0.0001). Our results suggest that the spasmolytic effect of the extract on rat uterus was mediated via voltage dependent calcium channels and β-adrenoceptors could also be involved in this action. Our results may support the use of black pepper in traditional medicine to relief the menorrhalgia.