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Effect of berberine on reperfusion arrhythmias was studied using a10min left anterior descending coronary artery occlusion followed by reperfusionin the isolated rat heart.Berberine when given 10min before coronary ligation re-duced the incidence of reperfusion arrhythmias in a dose-dependent manner.With10

-5

3.16×10

-5

and 10

-4

mol/L of berberine

ventricular fibrillation was reducedfrom its control incidence of 100% to 90%

70% and 40% （P

<

0.05） respectively.Heart rate was also reduced in a dose-dependent manner

falling from its controlvalue of 282±11 to 180±11 beats/min with the highest concentration of berberine.Coronary flow was increased in all berberine treated groups.With anantiarrhythmic dose of berberine (10

-4

mol/L)

hearts were paced （5 Hz） duringischemia period;under these conditions the anti-arrhythmic effect of berberinewas lost.When berberine (3.16×10

-5

and 10

-4

mol/L) was administered just beforereperfusion

no anti-arrhythmic effects were observed.The α-adrenoceptor antago-nist phentolamine (2.6×10

-5

mol/L) prevented reperfusion arrhythmias and ismuch more effective than berberine.These results suggest that the prophylatic ef-fects of berberine on reperfusion arrhythmias in the isolated rat heart are due toits negative chronotropic properties.