Background: Zizyphus spina Christi is a native plant of Iran. In traditional medicine, it is mainly used to wash hair. The present study was conducted to determine the effect of hydroacoholic Zizyphus spina christi leaf extract on perfused frog heart contractility and frequency.

Materials and Methods: It was an experimental study. The frog heart was cannulated through vena cava and then perfused with standard ringer solution. Having completed the oxygenation and feeding, the ringer solution was extracted through another cannulated tube via left branch of aorta. After recovery, the extract was added to reservoir to achieve the final concentrations of 0.625, 1.25, 2.5, 5, 10, and 20 mg/ml. Percentage changes of contractility and heart rates were recorded before and after adding the extract. Ringer solution, 20-22 degrees centigrade and PH=8.4 was kept on pressure of 5.5cmH2O as a constant venous pressure. For comparison, paired t-test and ANOVA were used.

Results: Twenty-five frogs have been studied. The extract could dose-dependently reduce the contractility and heart rate (p<0.0001). Concentration of 20 mg/ml in most cases caused cardiac arrest but contractility was restored by fresh Ringer's solution. Cardiac arrest was not affected by atrial electrical stimulation.

Conclusion: It seems as if the extract contains materials that disturb the usage of Ca²⁺ during contraction mechanism.