The cardiovascular activity of aqueous methanolic extract of Paspalidium flavidum L. was evaluated on isolated rabbit heart and aorta. Heart rates, force of contraction and perfusion pressure were assessed in the presence of different concentrations of extract and adrenaline by using Langendorff's technique. Moreover, the vasoconstriction effects were studied in rabbit aorta using isolated organ bath. The results indicated that the extract (1ng-100 μ g/ml) exhibited a significant increase in

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... rt rate, contractility and perfusion pressure of isolated rabbit's heart; with a maximum effect at 1ng/ml, which was comparable to adrenaline (1 μ g/ml). Similarly, adrenaline at doses from 1-10 μ g/ml produced a significant dose dependant increase in all the cardiac parameters. The cardiotonic effects of the extract were significantly blocked by propranolol (10(-5)M) while an increase in perfusion pressure was completely antagonized by verapamil (10(-6)M). Activity of cardiac marker enzymes was also significantly raised in the perfusate of isolated heart pretreated with the extract. In rabbit aorta, the extract exhibited a dose dependent vasoconstriction effect however it did not increase the tone of aorta when pre-treated with verapamil (10(-6)M). It is conceivable therefore; that the cardiotonic and vasoconstriction effects of the extract might be due to its agonistic actions on β-receptors and Ca(+2) channels.