AIM To study the early cardioprotective effects of pharmacological preconditioning of nitroglycerin (NG) and buprenorphine (BU) used alone and in combination on myocardial ischemia in rats. METHODS Male Wistar rats were randomized to 5 groups. The ischemia and reperfusion injury was induced by ligation of the left arterior descending coronary arrery for 30 min and followed reperfusion for 2 h. The rats were subjected to different treatments before I/R. Normal saline (NS) was infused intravenously with the same volume of NG and BU in Sham group. Ischemia/preconditioning (IP) was performed by three cycles of 5 min I/R in EIP group. BU (1 0 mg?kg -1 ) and NG (0 3 mg?kg -1 ) was administered intravenously alone in BU and NG group or given together in B+N group to mimic the effects of IP, respectively. Heart rate, blood pressure, ST segment and arrhythmias were recorded continuously throughout the whole test. Plasma LDH and CK were measured on 30 min after ischemia and 2 h after reperfusion, HE and TTC staining were performed to determine myocardial necrosis at the end of test. RESULTS Compared with Sham group the onset of arrhythmias was delayed and the duration of ventricular premature contraction (VPC) was shortened remarkably ( P