We investigated nerve growth factor precursor (proNGF) and mature NGF expression in ischemic and non-ischemic cortices after cerebral ischemia-reperfusion injury.In both ischemic and non-ischemic cortices, proNGF was found to be present in the extracellular space and cytoplasm.In addition, mature NGF was expressed in extracellular space, but with a very low signal.In ischemic cortex only, proNGF was significantly decreased, reaching a minimal level at 1 day.Mature NGF was increased at 4 hours, then reached a minimal level at 3 days.The p75 neurotrophin receptor (p75NTR) was significantly decreased after ischemia, and increased at 3 days after ischemia.These results confirmed that proNGF was the predominant form of NGF during the pathological process of cerebral ischemia-reperfusion injury.In addition, our findings suggest that ischemic injury may influence the conversion of proNGF to mature NGF, and that proNGF/p75NTR may be involved in reperfusion injury.