Inosine stimulates extensive axon collateral growth in the vat corticospinal tract after injury

The purine nucleoside inosine has been shown to induce axon outgrowth from primary neurons in culture through a direct intracellular mechanism. For th is study, we investigated the effects of inosine in vivo by examining wheth er it would stimulate axon growth after a unilateral transection of the cor ticospinal tract. Inosine applied with a minipump to the rat sensorimotor c ortex stimulated intact pyramidal cells to undergo extensive sprouting of t heir axons into the denervated spinal cord white matter and adjacent neurop il. Axon growth was visualized by anterograde tracing with biotinylated dex tran amine and by immunohistochemistry with antibodies to GAP-43. Thus, ino sine, a naturally occurring metabolite without known side effects, might he lp to restore essential circuitry after injury to the central nervous syste m.