A short episode of ischemia induced by coronary artery occlusion can precondition the myocardium against arrhythmia. The factors that have the potential to protect the myocardium from subsequent ischemia and reperfusion are controversial. In this study, the preconditioning-like effects of adrenaline were investigated in both anesthetized and conscious rats. Adrenaline 0.1 and 0.5 mg/kg or saline was administered 10 min before coronary occlusion in conscious and anesthetized rats. The 0.5 mg/kg dose of adrenaline decreased the total duration of arrhythmia in both models. The incidence of ventricular fibrillation decreased and survival rate increased only in conscious rats administered 0.5 mg/kg adrenaline. As a result, it is suggested that exogenous administration of adrenaline before coronary ligation may precondition and protect the heart against arrhythmia.