Rho is a member of the Rho family of small GTPase, and acts as a molecular switch in some signal transduction pathway. Rho can induce growth cones collapse and inhibit axonal outgrowth by regulating the actin cytoskeleton. Recent studies have indicated that three myelin-derived inhibitors including Nogo-A,MAG and OMgp all can inhibit axonal regeneration by activating the Rho-mediated signal transduction pathway.