This invention relates to methods for promoting myelination, neuronal survival, and oligodendrocyte differentiation and treating demyelination and dysmyelination disease by the administration of a TrkA antagonist. The invention also relates to methods of inhibiting or decreasing Sp35 expression by the use of a TrkA antagonist. Additionally, the invention relates generally to methods for blocking Sp35 and TrkA interaction and inhibiting or decreasing TrkA phosphorylation by the administration of a Sp35 antagonist.