Models to Evaluate Effects of Neurotrophic Factors on Axonal Regeneration

An injury to neural tissue that disrupts axonal continuity causes disconnection of pre- and postsynaptic elements of a neuronal circuit. The axon also transports to the cell body neurotrophic factors from the innervation territory, and axotomy, by interrupting this trophic supply, may lead to degeneration or death of the neuron unless supplementary trophic factors are available. Neural regeneration could be broadly defined as a process leading to the restitution of function in the damaged circuit. Such a process would involve, among other aspects, the maintenance of afferents to the presynaptic element, the regrowth of an axon, selection of and connection to the correct postsynaptic partner, and the promotion or restoration of downstream circuits to which this postsynaptic element contributes. Axonal regeneration, the topic of this chapter, is only concerned with the new growth of an axon in the direction of a putative postsynaptic partner.