The aim of this study was to examine the effects of fasudil, a Rho-kinase inhibitor, on ischemic preconditioning and carbachol preconditioning in anesthetized rats. The total number of ventricular ectopic beats was markedly augmented with fasudil at 0.3 mg/kg and depressed with fasudil at 10 mg/kg. Fasudil at 10 mg/kg also markedly decreased the ventricular tachycardia incidence. Ischemic preconditioning, induced by 5 min coronary artery occlusion and 5 min reperfusion, decreased the incidence of ventricular tachycardia and abolished the occurrence of ventricular fibrillation. The incidences of ventricular tachycardia and ventricular fibrillation in the fasudil (10 mg/kg) + ischemic preconditioning group were found to be similar to the ischemic preconditioning group. However, low doses of fasudil (0.3 and 1 mg/kg) appeared to prevent the antiarrhythmic effects of ischemic preconditioning. Carbachol (4 microg/kg/min for 5 min) induced marked reductions in mean arterial blood pressure, heart rate and abolished ventricular tachycardia. Marked reductions in ventricular ectopic beats and ventricular tachycardia were noted in the fasudil (10 mg/kg) + carbachol preconditioning group. Lactate levels were markedly reduced in the ischemic preconditioning group and this reduction was prominently inhibited with fasudil at 1 mg/kg. Ischemic preconditioning caused a marked decrease in plasma malondialdehyde levels. Fasudil (10 mg/kg), ischemic preconditioning and carbachol preconditioning each generated marked reductions in ischemic myocardial malondialdehyde levels. Decreases in infarct size were observed with fasudil (10 mg/kg) treatment, ischemic preconditioning and carbachol preconditioning when compared to control. These results suggest that low doses of fasudil (0.3 and 1 mg/kg) appeared to prevents the effects of ischemic preconditioning and carbachol preconditioning, but a high dose of fasudil (10 mg/kg) was able to produce cardioprotective effects on myocardium against arrhythmias, infarct size or biochemical parameters and mimic the effects of ischemic preconditioning in anesthetized rats.