To search for gene expression changes probably responsible for deafferentation-induced reorganization in the brain, we have analyzed the expression of mRNAs for ephrin-A1, -A2, -A3, -A5 and -B1 in the rat hippocampus following transection of the entorhinal afferents by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). We found that their expression in the deafferented hippocampus increased significantly by 7 days, reached the maximum at 14 days and almost recovered to control levels by 60 days post-lesion. It is notable that the up-regulation of ephrin mRNAs occurs during the reorganization in the deafferented hippocampus, suggesting that ephrins may be involved in the plasticity events of the adult brain after lesion.