The effect of sub-dural nerve tissue transplantation of the spinal cord of the rat.

The effects of sub-dural transplantation of autologous sciatic nerve on the dorsal columns of the rat was investigated. Combinations of the following procedures were used: 1 local X-irradiation with 4000 rad to suppress inherent remyelination activity; 2 small areas of primary demyelination induced by injection of lysolecithin or 6-aminonicotinamide; 3 transplantation of untreated or freeze-killed nerve, either teased or unteased. The lesions formed were examined for suppression of remyelination by local cells, remyelination by transplanted Schwann cells, deleterious effects of transplantation of the spinal cord, and the presence of suprapial nerve fibres. The following conclusions were drawn: 1 that 4000 rad of local X-irradiation suppresses inherent remyelination by oligodendroglia and local Schwann cells even when transplanted freeze-killed sciatic nerve is present; 2 that demyelinated axons can be remyelinated by Schwann cells from transplanted untreated nerve; 3 that the placing of peripheral nerve over the dorsal columns induces primary demyelination in both irradiated and non-irradiated animals; 4 that the placing of peripheral nerve over demyelinated locally X-irradiated spinal cord can lead to fibrous tissue invasion of the spinal cord and partial demyelination of the lateral and ventral columns; and 5 that transplantation of viable peripheral nerve onto the dorsal columns induces the formation of suprapial nerve fibres, which increase in number if demyelination or axonal damage is present in the dorsal columns. It seems probable, therefore, that elements in the peripheral nerve may exert trophic effects on dorsal column nerve fibres.