The present study was conducted to clarify the role of platelet-derived growth factor-B chain (PDGF-B) in neuronal death after ischemia. Transient forebrain ischemia was induced in Mongolian gerbils by occluding the bilateral carotid arteries for 5 min. We investigated PDGF-B expression in the hippocampus after ischemia by immunohistochemistry, Northern blotting and in situ hybridization histochemistry. The results showed that PDGF-B is expressed in control CA1 and CA3 neurons. In CA1, the amount of the PDGF-B transcript immediately increased, then disappeared 2 days after ischemia. Delayed neuronal death followed 1 day later. However, PDGF-B immunoreactivity in CA1 rapidly decreased and disappeared 12 h after transient forebrain ischemia, proceeding to delayed neuronal death. In contrast, the expression of both PDGF-B protein and the transcript was well preserved throughout the study in CA3, which remained viable even after ischemia. Accordingly, the selective neuronal susceptibility in the CA1 to ischemia corresponded with rapid disappearance of PDGF-B. PDGF-B expression may contribute to neuroprotective effect after ischemia.