The Cardiovascular effects of aqueous extract from the leaf of Tridax procumbens
were investigated on anaesthetized Sprague-Dawley rat. The intravenous administration of 3, 6, and 9mg/Kg of the aqueous extract caused significant decreases in the mean arterial blood pressure in a dose-related manner; i.e. the extract caused greater decrease in the mean arterial blood pressure at higher dose than at lower dose. Also, higher doses of the extract- 6mg/Kg and 9mg/Kg caused significant reductions in the heart rate while lower dose of the extract- 3mg/Kg did not cause any significant change in the heart rate. The hypotensive and the bradycardiac effects were immediate. The hypotensive effect of Tridax procumbens was inhibited by the pretreatment of the animal with atropine sulfate (1mg/kg). These results therefore seem to support the claim that the leaves of Tridax procumbens has hypotensive effect and that the mechanism of its action is possibly through activation of muscarinic cholinergic receptors.