RESUMO
Ipomoea carnea fam. Convolvulaceae is a poisonous plant and its toxicity is supposed to be due to the cardiac and respiratory failure. The present paper describes the cardiac effect of aqueous extract of the fresh leaves of I. carnea using mouse and frog heart. The aqueous extract produced an initial blockade of isolated frog heart for 5-10 sec followed by dose dependent increase in both amplitude and rate that lasts up to 2 min. Atropine (1 microgram/ml) blocked the initial depressant phase and potentiated the stimulant effect of the aqueous extract. The dose dependent increase in cardiac contractility of aqueous extract was not altered by propranolol or calcium channel blockers like nifedipine or diltiazem. The decrease in sodium chloride concentration or increase in potassium chloride concentration or calcium chloride concentration in physiological salt solution inhibited the responses to aqueous extract while an increase in sodium chloride concentration or decrease in potassium chloride or calcium chloride concentration in physiological salt solution potentiated the responses to the aqueous extract of I. carnea. It may be suggested from the data that aqueous extract of I. carnea produces positive inotropic effect on isolate frog heart possibly by sodium extrusion or release of the intracellular calcium.
