| Abstract | | There is a striking difference in the regenerative potential and the mechanisms of functional recovery between the central and the peripheral nervous system. While injured peripheral axons regenerate as a rule, there is little hope for successful growth of axons in the central nervous system. The aim of the present thesis was to determine the role of peripheral nerve components in axonal regeneration and to elucidate the mechanisms of transplantationinduced functional recovery and regeneration in the central nervous system. The models employed in these studies were the sciatic nerve and the nigrostriatal connections in the rat. Our results indicate that the success of peripheral nerve regeneration depends primarily on the preserved integrity of the basal lamina, which promotes and guides axonal growth. If continuity or functional integrity of the basal lamina are compromised, axonal growth is significantly slowed and the outcome of regeneration is unsatisfactory. Activated Schwann cells proximal and distal to a nerve injury can promote axonal growth, but are not prerequisite for regeneration. Putative tropic substances released by the denervated targets play a minor role in promoting axonal growth after crush injury. Transplantation into the central nervous system has been shown to induce functional recovery in the recipients. Mechanisms underlying this effect are not well understood. However, there is evidence that regenerative growth of the recipient connections may be involved. Our results suggest that, when adrenal medullary grafts are employed, the functional improvement may not be due to the release of dopamine or some specific trophic factors from the graft. Instead, the recipient response to the graft, involving the inflammatory and immune mediators, may play an important role.
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