[Changes of nerve growth factor (NGF) content in injured peripheral nerve during regeneration: local synthesis of NGF by Schwann cells].

NGF content in rat sciatic nerve was investigated using an enzyme immunoassay. Following nerve transection, NGF level increased at the distal side to transection. These NGF increases consisted of an initial rapid increase which might be due to retrograde axonal transport from peripheral organs, and also a secondly slow increase which appeared to be a result of local synthesis. Local synthesis of NGF in the nerve was confirmed by the findings that NGF content increased in the free segment between the two transection sites, and also in the cultured nerve segments where axonal transport could be neglected. Schwann cells and fibroblasts cultured from the sciatic nerve were found to secrete NGF suggesting the local synthesis of NGF by these cells in vivo. NGF accumulated by axonal transport and locally synthesized by non-neuronal cells in the distal side to transection, that is, the regenerating portion, might play an important role in nerve regeneration.