ABSTRACT
The contractile activity of M. pruriens and the relaxatory property of C. odorata was investigated using in vitro methods in the rat. M. pruriens caused a dose-dependent increase in uterine muscle contraction with a maximum peak in amplitude with 0.57 mg/ml of the extract and an EC50 of 2.7 mg/ml. The contraction was unaffected by atropine sulphate (0.042 µmol), but abolished by isoprenaline (0.06-0.23 µmol), salbutamol (0.012-0.4 µmol) and adrenaline (16 nmol).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 not able to abolish contractions stimulated by the extract however, 0.2 µmol of cyproheptadine caused 86% abolition of the extract –induced uterine contraction. The mechanism of Ca2+ mobilization in uterine muscle cells by M. pruriens isolated was also investigated in the rat. Uterine muscle contractions were significantly attenuated (100%; P < 0.01) in Ca2+-free physiological salt solution and in solutions containing verapamil (0.007- 0.14 mmol). Contractions stimulated by M. pruriens were unaffected by amiloride (1.1-2.1 µmol) in Ca2+-containing media. It is concluded that M.pruriens causes uterine muscle contraction by mobilizing external Ca2+ through a voltage-dependent Ca2+ channel. On the other hand, C. odorata caused a dose –dependent decrease in spontaneous contracting uterine tissue, giving an EC50 of 1.0 mg/ml. C. odorata was also able to decrease uterine contractions stimulated by acetylcholine ( 0.16-0.47 µmol), carbachol (1.6-7.8 µmol), oxytocin ( 2.6 x10-4 nmol), CaCl2 (0.1-1 mmol) -induced contractions and KCl (30 mmol) depolarized tissue. Propranolol (1 µmol) had no effect on C. odorata –induced relaxation. It is concluded that C. odorata causes relaxation via blockade of voltage operated calcium channels.
