Chapter 29 Mammalian root-spinal cord regeneration

Abstract

In adult mammals, it has been shown with modern morphological and histochemical techniques that regrowing nerve fibres in the dorsal root do not enter the spinal cord. This chapter describes the laboratory experiments on nerve fibre regeneration after dorsal root lesion and ventral root avulsion and medullar implantation. Experiments on dorsal root to spinal cord regrowth in the adult animals show that there is no difference in the regenerative capacity among neurons of different morphological, or neurochemical characteristics. The chapter suggests that regrowth of axons through the transition zone between the peripheral nervous system (PNS) and central nervous system (CNS) compartments at the root-spinal cord junction occurs after dorsal root severance in the immature animal and after ventral root avulsion injury and subsequent restoration of spinal cord-ventral root continuity. These findings appear to be encouraging examples of PNS-CNS neuronal regeneration. After an incomplete lesion, compensatory mechanisms like collateral sprouting from uninjured neurons, or neuronal neogenesis in the immature nervous system might influence the outcome of experiments and be misinterpreted as regeneration. Studies on root-spinal cord regeneration are therefore of great neurobiological and clinical importance.