Fig. 5. The effect of opioid antagonists on ischemic preconditioning. Infarct size (IS) expressed as a percentage of the area-at-risk (AAR). Infarct sizes in rat hearts subjected to control, NTD or NTD+IPC (naltrindole 5 mg/kg, intravenous; 10 min before ischemia or IPC), CTOP or CTOP+IPC (CTOP 1 mg/kg, intravenous; 10 min before ischemia or IPC), nor-BNI or nor-BNI+IPC (nor-binaltorphimine, 5 mg/kg, intravenous; 15 min before ischemia), ischemic preconditioning (IPC). Values are means ± SD. * P < 0.01 versus control; † P < 0.01 versus IPC.