Keeping in touch: sensory neurone regeneration in the CNS.

Adult neurones fail to regenerate when injured in the CNS, which leads to severe and irreversible functional deficits. Several important advances in understanding the reasons for this failure have been gained from the use of primary sensory neurones as a model system. The peripherally and centrally projecting branches of sensory neurones are differentially capable of regeneration, which is why these cells are ideally situated to elucidate the mechanisms that underlie regeneration failure. Such mechanisms include both a hostile environment within the spinal cord and a poor growth response following injury. For successful functional regeneration to occur, it is likely that both of these barriers will have to be surmounted, along with the challenge of guiding regrowing axons to appropriate postsynaptic targets. The contribution that the study of primary sensory neurones has made to the attainment of this goal will be reviewed.