C-Jun expression in the hippocampus of gerbils subjected to 5 min of transient forebrain ischemia was examined with immunohistochemistry and western blotting using two c-Jun antibodies raised against two different amino acid sequences. Both c-Jun antibodies showed increased immunoreactivity at 6 and 12 h postischemia in the stratum pyramidale of CA3 and granule cell layer of the dentate gyrus. No immunostaining was detected in CA1 up to the 7th day. Western blots showed increased c-Jun immunoreactivity at 6 and 12 h. However, the antibody c-Jun (AB-1) detected a single band at about p39 in normal and post-ischemic states, whereas the antibody c-Jun/AP-1 (N) recognized a band at about p39 in normal and post-ischemic gerbils, and a p62 phosphorylated double-band at 6 and 12 h following ischemia. In addition, increased c-Jun N-terminal kinase-1 (JNK-1) expression was observed on western blots at 6 and 12 h postischemia. These results suggest that different c-Jun-related responses, some of which probably indicate post-translational changes of the c-Jun protein, occur in the hippocampus of the gerbil following transient forebrain ischemia.