ABSTRACT
Axon injury is followed by a complex sequence of events: (1) cell body reaction, (2) axon sprouting and elongation, and (3) functional reinnervation of target. This sequence does not progress to completion for every injured neuron. The cell body reaction may result in death of the injured neuron; axon sprouting may be abortive, as in most instances of damage to the mature vertebrate central nervous system; regenerating axons may contact an inappropriate target. Nevertheless, in this essay I will review briefly the neuronal changes that occur at each stage of the successful regenerative sequence, with particular emphasis on the role of retrograde axonal transport in conveying to the cell body information about the status of the axon. Anterograde and retrograde transport are linked processes, since retrograde transport returns to the cell body materials originally reaching the axon by anterograde transport. Alterations in anterograde transport during regeneration will therefore be discussed where relevant to the issues of molecular information transfer within the neuron and the regulation of regeneration.
