Short duration cooling of the nerve to the extensor digitorum longus muscle of the rat in vivo induced partially reversible denervation of the muscle and atrophy in the type 2 muscle fibers. Increases in cAMP, cGMP phosphodiesterase, adenylate cyclase and guanylate cyclase were observed in the denervated muscle. A mixture of 4 bovine brain cortex gangliosides was used: gangliosides GM1, GD1a, GD1b and GT1. Treatment with gangliosides seemed to improve the excitability of the surviving motor units and to encourage recovery of neuromuscular trophic control. It did not affect the nerve conduction velocity or contractile properties of the denervated muscle.