Pathfinding and Synaptic Specificity of Regenerating Spinal Axons in the Lamprey
Recent developments in fetal CNS implantation and use of peripheral nerve bridges and grafts to circumvent a scar have led to optimism that regeneration of injured axons in the CNS may some day be used as a strategy in the treatment of CNS injuries (Björkland and Stenevi 1984; David and Aguayo 1981; Reier 1985; Reier et al. 1983 b). Spinal cord injuries are of particular concern because so much function passes through such a restricted cross-section of CNS and even relatively minor contusions often lead, via vascular reactions, to complete functional transection. Despite evidence of anatomical regeneration of fibers into the distal segments of spinal cord (David and Aguayo 1981; Bregman 1987), bridging and grafting experiments have not yet resulted in functional restoration in spinal cord-injured mammals. Unfortunately, it is difficult in such preparations to answer some fundamental questions concerning the fate of regenerating fibers. Do they conduct normal electrical impulses? Do they regenerate in a specific direction? Can they form physiologically functioning synapses with target neurons distal to the lesion? Are such synapses random or are they specific in some way which might lead to functional recovery? And finally, what guides the regenerating axon as it grows?
KeywordsSpinal Cord Growth Cone Axonal Regeneration Cell Pair Glial Process
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