Fig. 5. The effect of opioid antagonists on remifentanil preconditioning (RPC) or ischemic preconditioning (IPC). Lactate dehydrogenase (LDH) release in rat hearts subjected to control (CON), naltrindol (NTD, 5 × 10−6m), nor-binaltorphimine (BNI, 5 × 10−6m), CTOP (5 × 10−6m), RPC, IPC, NTD + RPC or IPC, BNI + RPC or IPC, and CTOP + RPC or IPC ( A – D ). Values are presented as mean ± SD. * P < 0.05, ** P < 0.01 versus control; † P < 0.05, †† P < 0.01 versus RPC or IPC.