Study On Lesion-Induced Structural Plasticity In The Central Nervous System

Transections of the entorhinal afferent fibers to hippocampus result in the denervation in specific hippocampal subregions, which is followed by a series of plastic reorganization events including glial activation, axonal sprouting, dendritic remodeling and reactive synaptogenesis. Many growth-associated molecules are thought to participate in these reorganization events. Since ephrins and their receptors Ephs have been shown to have important implications for the development of hippocampus, we studied in the present experiment the expression of these molecules in the deafferented hippocampus, expecting to find the potential functions of these molecules in the reorganization events. By using semiquantitative reverse transcription polymerase chain reaction (RT-PCR), the expression of mRNAs for ephrin-A1, A2, A3, A5 and B1 were analyzed in the rat hippocampus following transections of the entorhinal afferents. 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 upregulation of ephrin mRNAs occurs during the reorganization in the deafferented hippocampus, suggesting that ephrins may be involved in the plasticity...