A TrkB/EphrinA interaction controls retinal axon branching and synaptogenesis.
Transections of the entorhinal afferent fibers to hippocampus, perforant path (PP), result in the denervation in specific hippocampal subregions, which is followed by a series of plastic events including axon sprouting and reactive synaptogenesis. Many growth-associated molecules are thought to participate in these events. In the present study, we proved the upregulation of ephrin-A2 in the denervated areas of the ipsilateral hippocampus following PP transections. Interestingly, when the elevation of ephrin-A2 reached the maximum axon sprouting in the denervated areas almost finished, implying the possible inhibitory effect of ephrin-A2 on sprouting. In addition, ephrin-A2 expression was observed in synapses during reactive synaptogenesis, suggesting that this molecule might also be implicated in the formation and maturation of synapses in the denervated areas.