Axonal regeneration in the mammalian CNS

Axons in the adult central nervous system (CNS) of higher vertebrates are in general not capable of regeneration after injury. This is in contrast to the situation in lower vertebrates (fish and in part amphibia) and the mammalian peripheral nervous system (PNS), where severed axons can regenerate, correct synaptic connections can be formed again, and function can be restored. This enigma has been the subject of extensive studies in the last decades and a large amount of data has been accumulated. This article reviews recent developments in experimental approaches to axonal regrowth in the mammalian CNS focusing mostly on in-vivo systems.