Fig. 3. (A ) Ischemia limits recovery in phosphocreatine (PCr) (open squares ) and anesthetic preconditioning (APC) significantly improves recovery of PCr (closed squares ) during reperfusion in young adult hearts (*P < 0.05). (B ) Ischemia limits recovery in PCr (open circles ) and APC significantly improves recovery of PCr (closed circles ) during early reperfusion in middle-aged hearts (*P < 0.05). (C ) Ischemia causes a significant decrease in PCr (open triangles) and APC does not limit the decrease of PCr (closed triangles ) during ischemia and reperfusion in aged hearts. n = 6/group. * APC versus  control.