Keeping in touch: sensory neurone regeneration in the CNS

Adult neurones fail to regenerate when injured in the CNS, which leads to s evere and irreversible functional deficits. Several important advances in u nderstanding 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 regen eration, which is why these cells are ideally situated to elucidate the mec hanisms that underlie regeneration failure. Such mechanisms include both a hostile environment within the spinal cord and a poor growth response follo wing injury. For successful functional regeneration to occur, it is likely that both of these barriers will have to be surmounted, along with the chal lenge of guiding regrowing axons to appropriate postsynaptic targets. The c ontribution that the study of primary sensory neurones has made to the atta inment of this goal will be reviewed.