Endogenous synaptogenesis in the deafferented dentate gyrus does not exclude synapse formation by embryonic entorhinal transplants

Abstract

After partial deafferentation postsynaptic sites are reinnervated by local sprouting of remaining axons. We have investigated whether this process is sufficient to prevent new synapses being formed by transplanted embryonic tissue. We find that after unilateral entorhinal ablation endogenous sprouting by local axons is unable to reinnervate all the postsynaptic sites in the denervated outer dentate molecular layer. Axons from embryonic entorhinal tissue transplanted adjacent to the denervated area are able to reclaim a further proportion of the denervated postsynaptic sites. Thus, after a large lesion, endogenous sprouting is insufficient to preclude reinnervation by axons from embryonic transplants.